diff --git a/sc2/src/sc2code/sis.c b/sc2/src/sc2code/sis.c
index 87a870a87..1837596d6 100644
--- a/sc2/src/sc2code/sis.c
+++ b/sc2/src/sc2code/sis.c
@@ -1309,7 +1309,7 @@ SetFlashRect (PRECT pRect, FRAME f)
 	FRAME old_f;
 	int create_flash = 0;
 
-	if (! flash_mutex);
+	if (! flash_mutex)
 		flash_mutex = CreateMutex ();
 
 	old_r = flash_rect;