Index: binaries/data/mods/public/gui/gamesettings/attributes/MapExploration.js
===================================================================
--- binaries/data/mods/public/gui/gamesettings/attributes/MapExploration.js
+++ binaries/data/mods/public/gui/gamesettings/attributes/MapExploration.js
@@ -34,20 +34,32 @@
 
 	setExplored(enabled)
 	{
-		this.explored = enabled;
-		this.revealed = this.revealed && this.explored;
+		// Check if enabled is defined in map settings - don't change any values if it isn't.
+		if(enabled !== undefined)
+		{
+			this.explored = enabled;
+			this.revealed = this.revealed && this.explored;
+		}
 	}
 
 	setRevealed(enabled)
 	{
-		this.explored = this.explored || enabled;
-		this.revealed = enabled;
-		this.allied = this.allied || enabled;
+		// Check if enabled is defined in map settings - don't change any values if it isn't.
+		if(enabled !== undefined)
+		{
+			this.explored = this.explored || enabled;
+			this.revealed = enabled;
+			this.allied = this.allied || enabled;
+		}
 	}
 
 	setAllied(enabled)
 	{
-		this.allied = enabled;
-		this.revealed = this.revealed && this.allied;
+		// Check if enabled is defined in map settings - don't change any values if it isn't.
+		if(enabled !== undefined)
+		{
+			this.allied = enabled;
+			this.revealed = this.revealed && this.allied;
+		}
 	}
 };