1 files changed, 5 insertions, 2 deletions

diff --git a/src/fns.c b/src/fns.c
index 0fded92aeb2..6aad119d1f9 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -159,14 +159,14 @@ EMACS_INT length_internal (Lisp_Object sequence, int len)
   if (len < 0xffff)
     while (CONSP (sequence))
       {
-        if (--len == 0)
+        if (--len <= 0)
           return -1;
         sequence = XCDR (sequence);
       }
   /* Signal an error on circular lists. */
   else
     FOR_EACH_TAIL (sequence)
-      if (--len == 0)
+      if (--len <= 0)
         return -1;
   return len;
 }
@@ -210,6 +210,9 @@ counted.  */)
   CHECK_FIXNUM (length);
   EMACS_INT len = XFIXNUM (length);
 
+  if (len < 0)
+    return Qnil;
+
   if (CONSP (sequence))
     return length_internal (sequence, len + 1) == 1? Qt: Qnil;
   else