diff --git a/function.c b/function.c
index 830624d..246974d 100644
--- a/function.c
+++ b/function.c
@@ -341,6 +341,10 @@ void function_set_desc( const wchar_t *name, const wchar_t *desc )
 static int al_contains_str( array_list_t *list, const wchar_t * str )
 {
 	int i;
+
+	CHECK( list, 0 );
+	CHECK( str, 0 );
+	
 	for( i=0; i<al_get_count( list ); i++ )
 	{
 		if( wcscmp( al_get( list, i ), str) == 0 )