diff --git a/sp/src/tier1/KeyValues.cpp b/sp/src/tier1/KeyValues.cpp
index 19d6d66c..16fae59c 100644
--- a/sp/src/tier1/KeyValues.cpp
+++ b/sp/src/tier1/KeyValues.cpp
@@ -2081,6 +2081,28 @@ bool EvaluateConditional( const char *str )
 
 	if ( Q_stristr( str, "$POSIX" ) )
 		return IsPosix() ^ bNot;
+
+#ifdef MAPBASE
+	// Custom conditional
+	switch( str[bNot ? 1 : 0] )
+	{
+		case '%':
+		{
+			// Look for a cvar
+			ConVarRef cvar( str + (bNot ? 2 : 1), true );
+			if (cvar.IsValid())
+			{
+				return cvar.GetBool() ^ bNot;
+			}
+		} break;
+
+		case '-':
+		{
+			// Look for a command line param
+			return (CommandLine()->CheckParm( bNot ? str+1 : str ) != 0) ^ bNot;
+		} break;
+	}
+#endif
 	
 	return false;
 }