1 files changed, 2 insertions, 0 deletions

diff --git a/src/data.c b/src/data.c
index 6f1256786ec..6b1a9fc8860 100644
--- a/src/data.c
+++ b/src/data.c
@@ -3231,10 +3231,12 @@ syms_of_data ()
   DEFVAR_LISP ("most-positive-fixnum", &Vmost_positive_fixnum,
                doc: /* The largest value that is representable in a Lisp integer.  */);
   Vmost_positive_fixnum = make_number (MOST_POSITIVE_FIXNUM);
+  XSYMBOL (intern ("most-positive-fixnum"))->constant = 1;
 
   DEFVAR_LISP ("most-negative-fixnum", &Vmost_negative_fixnum,
                doc: /* The smallest value that is representable in a Lisp integer.  */);
   Vmost_negative_fixnum = make_number (MOST_NEGATIVE_FIXNUM);
+  XSYMBOL (intern ("most-negative-fixnum"))->constant = 1;
 }
 
 SIGTYPE