1 files changed, 2 insertions, 2 deletions
diff --git a/gc.c b/gc.c
index df9e919655..f070b11b64 100644
--- a/gc.c
+++ b/gc.c
@@ -2279,8 +2279,8 @@ static void
 should_be_callable(VALUE block)
 {
     if (!rb_obj_respond_to(block, rb_intern("call"), TRUE)) {
-	rb_raise(rb_eArgError, "wrong type argument %s (should be callable)",
-		 rb_obj_classname(block));
+	rb_raise(rb_eArgError, "wrong type argument %"PRIsVALUE" (should be callable)",
+		 rb_obj_class(block));
     }
 }
 static void