1 files changed, 1 insertions, 1 deletions
diff --git a/thread.c b/thread.c
index 4fbc14d86c..4ab0788534 100644
--- a/thread.c
+++ b/thread.c
@@ -2978,7 +2978,7 @@ rb_mutex_unlock(VALUE self)
     GetMutexPtr(self, mutex);
 
     err = mutex_unlock(mutex);
-    if (err) rb_raise(rb_eThreadError, err);
+    if (err) rb_raise(rb_eThreadError, "%s", err);
 
     return self;
 }