diff --git a/simulator-primitives.rkt b/simulator-primitives.rkt
index 087de4e..6eefa7c 100644
--- a/simulator-primitives.rkt
+++ b/simulator-primitives.rkt
@@ -116,6 +116,7 @@
                                                     
                                                      symbol->string
                                                      string-append
+                                                     string-length
                                                      
                                                      (my-cons cons)
                                                      (my-list list)
diff --git a/tests/conform/program0.sch b/tests/conform/program0.sch
index 8c99991..9fbe3d9 100644
--- a/tests/conform/program0.sch
+++ b/tests/conform/program0.sch
@@ -37,6 +37,12 @@
       (add1 (length (cdr l)))))
 
 
+(define (append l1 l2)
+  (if (null? l1) 
+      l2
+      (cons (car l1) (append (cdr l1) l2))))
+
+
 (define vector-copy
   (lambda (v)
     (let ((length (vector-length v)))