(Fexpt): Use floats for negative exponent.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/floatfns.c b/src/floatfns.c
index 529e7b76e39..cbcc0bfe520 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -460,7 +460,8 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
   CHECK_NUMBER_OR_FLOAT (arg1);
   CHECK_NUMBER_OR_FLOAT (arg2);
   if (INTEGERP (arg1)     /* common lisp spec */
-      && INTEGERP (arg2)) /* don't promote, if both are ints */
+      && INTEGERP (arg2)   /* don't promote, if both are ints, and */
+      && 0 <= XINT (arg2)) /* we are not computing the -ARG2 root */
     {                           /* this can be improved by pre-calculating */
       EMACS_INT acc, x, y;      /* some binary powers of x then accumulating */
       Lisp_Object val;