MLKCons: Do not crash when displaying a cons whose cdr is a fixnum.

1 files changed, 2 insertions, 2 deletions

diff --git a/MLKCons.m b/MLKCons.m
index bee917f..9e49d45 100644
--- a/MLKCons.m
+++ b/MLKCons.m
@@ -146,7 +146,7 @@
   if (!_cdr)
     return [NSString stringWithFormat:@"%@",
                      MLKPrintToString(_car)];
-  else if ([_cdr isKindOfClass:[MLKCons class]])
+  else if (MLKInstanceP (_cdr) && [_cdr isKindOfClass:[MLKCons class]])
     return [NSString stringWithFormat:@"%@ %@",
                      MLKPrintToString(_car),
                      [_cdr bareDescriptionForLisp]];
@@ -158,7 +158,7 @@
 
 -(NSString *)descriptionForLisp
 {
-  if ([_cdr isKindOfClass:[MLKCons class]])
+  if (MLKInstanceP (_cdr) && [_cdr isKindOfClass:[MLKCons class]])
     {
       if (_car == [[MLKPackage findPackage:@"COMMON-LISP"] intern:@"QUOTE"])
         return [NSString stringWithFormat:@"'%@", [_cdr bareDescriptionForLisp]];