diff --git a/ChangeLog b/ChangeLog
index 549641f3c6..1254a3aaec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Nov  4 13:03:00 2016  Kenta Murata  <mrkn@mrkn.jp>
+
+	* numeric.c (rb_int_digits): Fix exception message
+
 Fri Nov  4 10:51:16 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/pathname/pathname.c (path_hash): fix unnormalized Fixnum
diff --git a/numeric.c b/numeric.c
index d317d046c6..00a1050f43 100644
--- a/numeric.c
+++ b/numeric.c
@@ -4680,7 +4680,9 @@ rb_int_digits(int argc, VALUE *argv, VALUE num)
             return rb_int_digits_bigbase(num, base_value);
 
         base = FIX2LONG(base_value);
-        if (base < 2)
+        if (base < 0)
+            rb_raise(rb_eArgError, "negative radix");
+        else if (base < 2)
             rb_raise(rb_eArgError, "invalid radix %ld", base);
     }
     else