(concat): Take modulus of thisindex before shifting.

Declare thisindex as unsigned.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/fns.c b/src/fns.c
index 1c7a98cae46..7991403eea4 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -409,7 +409,7 @@ concat (nargs, args, target_type, last_special)
     {
       Lisp_Object thislen;
       int thisleni;
-      register int thisindex = 0;
+      register unsigned int thisindex = 0;
 
       this = args[argnum];
       if (!CONSP (this))
@@ -443,7 +443,7 @@ concat (nargs, args, target_type, last_special)
                        / BITS_PER_CHAR);
                   int byte;
                   byte = XBOOL_VECTOR (val)->data[thisindex / BITS_PER_CHAR];
-                  if (byte & (1 << thisindex))
+                  if (byte & (1 << (thisindex % BITS_PER_CHAR)))
                     elt = Qt;
                   else
                     elt = Qnil;