diff --git a/res/res_musiconhold.c b/res/res_musiconhold.c
index ade8d5325551e78847838db927c4ded2db1e8990..01920e087547bdccbb42ba9302a26394063b1a59 100644
--- a/res/res_musiconhold.c
+++ b/res/res_musiconhold.c
@@ -186,8 +186,8 @@ static struct ao2_container *mohclasses;
 
 static int reload(void);
 
-#define mohclass_ref(class,string)   (ao2_t_ref((class), +1, string), class)
-#define mohclass_unref(class,string) (ao2_t_ref((class), -1, string), (struct mohclass *) NULL)
+#define mohclass_ref(class,string)   (ao2_t_ref((class), +1, (string)), class)
+#define mohclass_unref(class,string) (ao2_t_ref((class), -1, (string)), (struct mohclass *) NULL)
 
 static void moh_files_release(struct ast_channel *chan, void *data)
 {