1 files changed, 1 insertions, 1 deletions
diff --git a/numeric.c b/numeric.c
index 3ceb5ae2d2..ddc909ee28 100644
--- a/numeric.c
+++ b/numeric.c
@@ -332,7 +332,7 @@ num_sadded(VALUE x, VALUE name)
 static VALUE
 num_init_copy(VALUE x, VALUE y)
 {
-    rb_raise(rb_eTypeError, "can't copy %s", rb_obj_classname(x));
+    rb_raise(rb_eTypeError, "can't copy %"PRIsVALUE, rb_obj_class(x));
 
     UNREACHABLE;
 }