1 files changed, 4 insertions, 0 deletions
diff --git a/rational.c b/rational.c
index 86c33b539c..6cd31e119a 100644
--- a/rational.c
+++ b/rational.c
@@ -1285,6 +1285,10 @@ f_round_common(int argc, VALUE *argv, VALUE self, VALUE (*func)(VALUE))
 	return self;
     }
 
+    if (!k_rational_p(s)) {
+	s = f_rational_new_bang1(CLASS_OF(self), s);
+    }
+
     s = (*func)(s);
 
     s = f_div(f_rational_new_bang1(CLASS_OF(self), s), b);