1 files changed, 1 insertions, 1 deletions
diff --git a/ruby.c b/ruby.c
index 8b4688254d..2b2e548de8 100644
--- a/ruby.c
+++ b/ruby.c
@@ -765,7 +765,7 @@ set_option_encoding_once(const char *type, VALUE *name, const char *e, long elen
     if (*name &&
 	rb_funcall(ename, rb_intern("casecmp"), 1, *name) != INT2FIX(0)) {
 	rb_raise(rb_eRuntimeError,
-		 "%s already set to %s", type, RSTRING_PTR(*name));
+		 "%s already set to %"PRIsVALUE, type, *name);
     }
     *name = ename;
 }