diff --git a/include/tclap/SwitchArg.h b/include/tclap/SwitchArg.h
index dc4952e..3961e35 100644
--- a/include/tclap/SwitchArg.h
+++ b/include/tclap/SwitchArg.h
@@ -197,7 +197,15 @@ inline bool SwitchArg::processArg(int *i, std::vector<std::string>& args)
 			ret = true;
 
 		if ( _alreadySet || ( !ret && combinedSwitchesMatch( args[*i] ) ) )
-			throw(CmdLineParseException("Argument already set!", toString()));	
+		{
+			if ( _xorSet )
+				throw(CmdLineParseException(
+				      "Mutually exclusive argument already set!", 
+				                            toString()));
+			else
+				throw(CmdLineParseException("Argument already set!", 
+				                            toString()));	
+		}
 
 		_alreadySet = true;
 
diff --git a/include/tclap/ValueArg.h b/include/tclap/ValueArg.h
index 28117f6..dbaf3bf 100644
--- a/include/tclap/ValueArg.h
+++ b/include/tclap/ValueArg.h
@@ -335,7 +335,15 @@ bool ValueArg<T>::processArg(int *i, std::vector<std::string>& args)
     if ( argMatches( flag ) )
     {
         if ( _alreadySet )
-			throw( CmdLineParseException("Argument already set!", toString()) );
+		{
+			if ( _xorSet )
+				throw( CmdLineParseException(
+				       "Mutually exclusive argument already set!", 
+				                             toString()) );
+			else
+				throw( CmdLineParseException("Argument already set!", 
+				                             toString()) );
+		}
 
         if ( Arg::delimiter() != ' ' && value == "" )
 			throw( ArgParseException( 
diff --git a/tests/test22.out b/tests/test22.out
index 77ee1c8..76153be 100644
--- a/tests/test22.out
+++ b/tests/test22.out
@@ -1,5 +1,5 @@
 PARSE ERROR: Argument: -b (--bbb)
-             Argument already set!
+             Mutually exclusive argument already set!
 
 Brief USAGE: 
    ../examples/test5  {-a <string>|-b <string>} {--eee <string>|--fff
diff --git a/tests/test24.out b/tests/test24.out
index 77ee1c8..76153be 100644
--- a/tests/test24.out
+++ b/tests/test24.out
@@ -1,5 +1,5 @@
 PARSE ERROR: Argument: -b (--bbb)
-             Argument already set!
+             Mutually exclusive argument already set!
 
 Brief USAGE: 
    ../examples/test5  {-a <string>|-b <string>} {--eee <string>|--fff