1 files changed, 4 insertions, 3 deletions
diff --git a/bignum.c b/bignum.c
index db7215ac15..7bcc4c7935 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1210,10 +1210,11 @@ rb_big2ulong(VALUE x)
     VALUE num = big2ulong(x, "unsigned long", TRUE);
 
     if (!RBIGNUM_SIGN(x)) {
-	if ((long)num < 0) {
+	VALUE v = (VALUE)(-(SIGNED_VALUE)num);
+
+	if (v <= LONG_MAX)
 	    rb_raise(rb_eRangeError, "bignum out of range of unsigned long");
-	}
-	return (VALUE)(-(SIGNED_VALUE)num);
+	return v;
     }
     return num;
 }