diff --git a/ChangeLog b/ChangeLog
index 4b80bd4396..21f8d0efd5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Sep 12 05:35:24 2015  Eric Wong  <e@80x24.org>
+
+	* rational.c (string_to_r_strict): preserve encoding in exception
+
 Fri Sep 11 20:23:35 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_core.h: remove rb_call_info_t::aux.opt_pc.
diff --git a/rational.c b/rational.c
index 2d0daea2e3..0f3167a7e0 100644
--- a/rational.c
+++ b/rational.c
@@ -2327,9 +2327,8 @@ string_to_r_strict(VALUE self)
 	s = (char *)"";
 
     if (!parse_rat(s, 1, &num)) {
-	VALUE ins = f_inspect(self);
-	rb_raise(rb_eArgError, "invalid value for convert(): %s",
-		 StringValuePtr(ins));
+	rb_raise(rb_eArgError, "invalid value for convert(): %+"PRIsVALUE,
+		 self);
     }
 
     if (RB_TYPE_P(num, T_FLOAT))