1 files changed, 1 insertions, 1 deletions
diff --git a/vm.c b/vm.c
index e963225ae8..fc58d07c6d 100644
--- a/vm.c
+++ b/vm.c
@@ -1681,7 +1681,7 @@ thread_free(void *ptr)
 	    rb_bug("thread_free: locking_mutex must be NULL (%p:%ld)", (void *)th, th->locking_mutex);
 	}
 	if (th->keeping_mutexes != NULL) {
-	    rb_bug("thread_free: keeping_mutexes must be NULL (%p:%ld)", (void *)th, th->locking_mutex);
+	    rb_bug("thread_free: keeping_mutexes must be NULL (%p:%p)", (void *)th, th->keeping_mutexes);
 	}
 
 	if (th->local_storage) {