diff --git a/src/mailman.scm b/src/mailman.scm
index ae18bc5..250e077 100644
--- a/src/mailman.scm
+++ b/src/mailman.scm
@@ -180,10 +180,12 @@
 		 (mailman-compare-members ml emails)))
      (let ((listname (mailman-list-name ml)))
        (let loop ((emails missing))
-	 (add-email-to-mailman-list listname (car emails))
-	 (loop (cdr emails)))
+	 (when (not (null? emails))
+	   (add-email-to-mailman-list listname (car emails))
+	   (loop (cdr emails))))
        (let loop ((emails surplus))
-	 (remove-email-from-mailman-list listname (car emails))
-	 (loop (cdr loop))))))
+	 (when (not (null? emails))
+	   (remove-email-from-mailman-list listname (car emails))
+	   (loop (cdr loop)))))))
 
  )