diff --git a/storage/innodb_plugin/include/sync0rw.h b/storage/innodb_plugin/include/sync0rw.h
index aedfd5f3f86..630f6c30138 100644
--- a/storage/innodb_plugin/include/sync0rw.h
+++ b/storage/innodb_plugin/include/sync0rw.h
@@ -429,8 +429,9 @@ ibool
 rw_lock_own(
 /*========*/
 	rw_lock_t*	lock,		/*!< in: rw-lock */
-	ulint		lock_type);	/*!< in: lock type: RW_LOCK_SHARED,
+	ulint		lock_type)	/*!< in: lock type: RW_LOCK_SHARED,
 					RW_LOCK_EX */
+	__attribute__((warn_unused_result));
 #endif /* UNIV_SYNC_DEBUG */
 /******************************************************************//**
 Checks if somebody has locked the rw-lock in the specified mode. */
diff --git a/storage/innodb_plugin/include/sync0sync.h b/storage/innodb_plugin/include/sync0sync.h
index b93a8d1c080..d470b823fc3 100644
--- a/storage/innodb_plugin/include/sync0sync.h
+++ b/storage/innodb_plugin/include/sync0sync.h
@@ -206,7 +206,8 @@ UNIV_INTERN
 ibool
 mutex_own(
 /*======*/
-	const mutex_t*	mutex);	/*!< in: mutex */
+	const mutex_t*	mutex)	/*!< in: mutex */
+	__attribute__((warn_unused_result));
 #endif /* UNIV_DEBUG */
 #ifdef UNIV_SYNC_DEBUG
 /******************************************************************//**