diff --git a/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/GameServer.java
index 2aed7d117a..335962530a 100644
--- a/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -468,6 +470,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index 1663807336..4553db855c 100644
--- a/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_01.0_Ertheia/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7393,16 +7393,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7604,22 +7594,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/GameServer.java
index 4feb00d33d..d499bbddd0 100644
--- a/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -476,6 +478,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index 97147f01a0..f5f0ee0ff3 100644
--- a/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_02.5_Underground/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7396,16 +7396,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7607,22 +7597,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/GameServer.java
index 4feb00d33d..d499bbddd0 100644
--- a/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -476,6 +478,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index 73b9cc2a90..e77ccc2b2c 100644
--- a/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_03.0_Helios/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7398,16 +7398,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7609,22 +7599,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/GameServer.java
index 667c9e9dc6..dfd90ff9be 100644
--- a/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -476,6 +478,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index cea81c5657..fe2b70914d 100644
--- a/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_04.0_GrandCrusade/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7393,16 +7393,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7604,22 +7594,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/GameServer.java
index fc2f9a71e1..1c3fc93079 100644
--- a/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -480,6 +482,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index 2d8a670291..69cf1945d0 100644
--- a/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_05.0_Salvation/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7375,16 +7375,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7586,22 +7576,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/GameServer.java
index fc2f9a71e1..1c3fc93079 100644
--- a/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -480,6 +482,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index 2d90f774be..6ee073eb12 100644
--- a/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_05.5_EtinasFate/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7375,16 +7375,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7586,22 +7576,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/GameServer.java
index fafc620465..4d9866e8bc 100644
--- a/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -482,6 +484,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index a69072b215..d06f76f3b2 100644
--- a/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_06.0_Fafurion/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7376,16 +7376,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7587,22 +7577,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/GameServer.java
index 9d7e00eafd..b44ce218b5 100644
--- a/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -488,6 +490,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index d7221a1750..65e6690344 100644
--- a/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_07.0_PreludeOfWar/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7390,16 +7390,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7601,22 +7591,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/GameServer.java
index f653b10017..e2a212c71f 100644
--- a/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -488,6 +490,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index 1c572ca1e8..549d2a081d 100644
--- a/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_08.2_Homunculus/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7492,16 +7492,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7703,22 +7693,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{
diff --git a/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/GameServer.java b/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/GameServer.java
index 2a435512a6..f8c8f6f1b6 100644
--- a/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/GameServer.java
+++ b/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/GameServer.java
@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.lang.management.ManagementFactory;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.time.Duration;
 import java.util.Calendar;
 import java.util.logging.Level;
@@ -490,6 +492,24 @@ public class GameServer
 		LoginServerThread.getInstance().start();
 		
 		Toolkit.getDefaultToolkit().beep();
+		
+		// TODO: Remove this.
+		// Old dualclass system adjustment.
+		if (!GlobalVariablesManager.getInstance().getBoolean("DUALCLASS_SYSTEM_UPDATED", false))
+		{
+			GlobalVariablesManager.getInstance().set("DUALCLASS_SYSTEM_UPDATED", true);
+			try (Connection con = DatabaseFactory.getConnection();
+				PreparedStatement ps1 = con.prepareStatement("DELETE from character_variables WHERE var='KNOWN_DUAL_SKILLS'");
+				PreparedStatement ps2 = con.prepareStatement("DELETE from character_skills WHERE skill_id in (19222, 19223, 19224, 19225, 19226, 19229, 19290)"))
+			{
+				ps1.execute();
+				ps2.execute();
+			}
+			catch (Exception e)
+			{
+				LOGGER.warning(e.getMessage());
+			}
+		}
 	}
 	
 	public long getStartedTime()
diff --git a/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java b/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
index ecd109c11f..71343ef3e2 100644
--- a/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
+++ b/L2J_Mobius_09.2_ReturnOfTheQueenAnt/java/org/l2jmobius/gameserver/model/actor/instance/PlayerInstance.java
@@ -7518,16 +7518,6 @@ public class PlayerInstance extends Playable
 			storeSkill(newSkill, oldSkill, -1);
 			if (CommonUtil.contains(DUAL_CLASS_SKILLS, newSkill.getId()))
 			{
-				// Old system compatibility.
-				if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-				{
-					getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-					for (int skillId : DUAL_CLASS_SKILLS)
-					{
-						removeSkill(skillId);
-					}
-				}
-				
 				final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 				knownSkills.put(newSkill.getId(), newSkill.getLevel());
 				getVariables().setIntegerMap(KNOWN_DUAL_SKILLS_VAR, knownSkills);
@@ -7729,22 +7719,12 @@ public class PlayerInstance extends Playable
 	}
 	
 	/**
-	* Learn known dualclass skills.
-	*/
+	 * Learn known dualclass skills.
+	 */
 	public void restoreDualSkills()
 	{
 		if (isDualClassActive() || !isSubClassActive())
 		{
-			// Old system compatibility.
-			if (getVariables().getString(KNOWN_DUAL_SKILLS_VAR, "").contains("("))
-			{
-				getVariables().set(KNOWN_DUAL_SKILLS_VAR, "");
-				for (int skillId : DUAL_CLASS_SKILLS)
-				{
-					removeSkill(skillId);
-				}
-			}
-			
 			final Map<Integer, Integer> knownSkills = getVariables().getIntegerMap(KNOWN_DUAL_SKILLS_VAR);
 			if (knownSkills.isEmpty())
 			{