diff --git a/mes.c b/mes.c
index 4b099afe..54faf6dc 100644
--- a/mes.c
+++ b/mes.c
@@ -1168,6 +1168,14 @@ divide (scm *x/*...*/)
   return make_number (n);
 }
 
+scm *
+modulo (scm *a, scm *b)
+{
+  assert (a->type == NUMBER);
+  assert (b->type == NUMBER);
+  return make_number (a->value % b->value);
+}
+
 scm *
 multiply (scm *x/*...*/)
 {
diff --git a/scm.mes b/scm.mes
index e4520e8e..57afb211 100755
--- a/scm.mes
+++ b/scm.mes
@@ -174,6 +174,8 @@
   (or (> a b)
       (= a b)))
 
+(define quotient /)
+
 (define (list? x)
   (or (null? x)
       (and (pair? x) (list? (cdr x)))))