diff --git a/engine/client/cl_gameui.c b/engine/client/cl_gameui.c
index 54a48ea2..4b4d8945 100644
--- a/engine/client/cl_gameui.c
+++ b/engine/client/cl_gameui.c
@@ -1303,6 +1303,16 @@ static gameinfo2_t *pfnGetModInfo( int gi_version, int i )
 	return &gameui.modsInfo[i];
 }
 
+static int pfnIsCvarReadOnly( const char *name )
+{
+	convar_t *cv = Cvar_FindVar( name );
+
+	if( !cv )
+		return -1;
+
+	return FBitSet( cv->flags, FCVAR_READ_ONLY ) ? 1 : 0;
+}
+
 static ui_extendedfuncs_t gExtendedfuncs =
 {
 	pfnEnableTextInput,
@@ -1318,6 +1328,7 @@ static ui_extendedfuncs_t gExtendedfuncs =
 	&gNetApi,
 	pfnGetGameInfo,
 	pfnGetModInfo,
+	pfnIsCvarReadOnly,
 };
 
 void UI_UnloadProgs( void )
diff --git a/engine/menu_int.h b/engine/menu_int.h
index 8dd840c4..5b9fb429 100644
--- a/engine/menu_int.h
+++ b/engine/menu_int.h
@@ -222,6 +222,10 @@ typedef struct ui_extendedfuncs_s {
 	// new mods info
 	gameinfo2_t *(*pfnGetGameInfo)( int gi_version ); // might return NULL if gi_version is unsupported
 	gameinfo2_t *(*pfnGetModInfo)( int gi_version, int mod_index ); // continiously call it until it returns null
+
+	// returns 1 if cvar has read-only flag
+	// or -1 if cvar not found
+	int (*pfnIsCvarReadOnly)( const char *name );
 } ui_extendedfuncs_t;
 
 // deprecated export from old engine