diff --git a/dlls/dmsynth/dmsynth_main.c b/dlls/dmsynth/dmsynth_main.c
index 1fb51573d2b..9568cb6bd08 100644
--- a/dlls/dmsynth/dmsynth_main.c
+++ b/dlls/dmsynth/dmsynth_main.c
@@ -360,7 +360,7 @@ const char *debugstr_dmguid (const GUID *id) {
 
         if (!id) return "(null)";
 
-	for (i = 0; i < sizeof(guids)/sizeof(guids[0]); i++) {
+	for (i = 0; i < ARRAY_SIZE(guids); i++) {
 		if (IsEqualGUID(id, guids[i].guid))
 			return guids[i].name;
 	}