1 files changed, 1 insertions, 1 deletions
diff --git a/string.c b/string.c
index 49f3ba9456..983f3e682a 100644
--- a/string.c
+++ b/string.c
@@ -957,7 +957,7 @@ rb_str_times(VALUE str, VALUE times)
 static VALUE
 rb_str_format_m(VALUE str, VALUE arg)
 {
-    VALUE tmp = rb_check_array_type(arg);
+    volatile VALUE tmp = rb_check_array_type(arg);
 
     if (!NIL_P(tmp)) {
 	return rb_str_format(RARRAY_LEN(tmp), RARRAY_PTR(tmp), str);