diff --git a/kmod/src/msg.h b/kmod/src/msg.h
index 64376f9a..8e53290f 100644
--- a/kmod/src/msg.h
+++ b/kmod/src/msg.h
@@ -1,8 +1,8 @@
 #ifndef _SCOUTFS_MSG_H_
 #define _SCOUTFS_MSG_H_
 
-void scoutfs_msg(struct super_block *sb, const char *prefix, const char *str,
-		 const char *fmt, ...);
+void __printf(4, 5) scoutfs_msg(struct super_block *sb, const char *prefix,
+				const char *str, const char *fmt, ...);
 
 #define scoutfs_err(sb, fmt, args...) \
 	scoutfs_msg(sb, KERN_ERR, " error", fmt, ##args)