1 files changed, 2 insertions, 0 deletions
diff --git a/liblali.c b/liblali.c
index 6696bc3..54c4bfd 100644
--- a/liblali.c
+++ b/liblali.c
@@ -1180,6 +1180,8 @@ Object *primitiveJoin(Object **args, GC_PARAM) {
     for (;;) {
       lcar = list->car;
       for (;;) {
+        if (lcar->car->string[2] != '\0')
+          exceptionWithObject((*args)->car, "only can join with 1-digit number elements");
         noPrefixNumber[0] = lcar->car->string[1];
         noPrefixNumber[1] = '\0';
         strcat(result, noPrefixNumber);