1 files changed, 1 insertions, 0 deletions
diff --git a/arith.c b/arith.c
index 79fb26d0..ccc29657 100644
--- a/arith.c
+++ b/arith.c
@@ -360,6 +360,7 @@ val minus(val anum, val bnum)
 
   switch (TAG_PAIR(tag_a, tag_b)) {
   case TAG_PAIR(TAG_NUM, TAG_NUM): 
+  case TAG_PAIR(TAG_CHR, TAG_CHR): 
     {
       cnum a = c_num(anum);
       cnum b = c_num(bnum);