diff --git a/static/js/message_edit.js b/static/js/message_edit.js
index 87dbb7d8c1..ca589641cd 100644
--- a/static/js/message_edit.js
+++ b/static/js/message_edit.js
@@ -244,7 +244,8 @@ function edit_message(row, raw_content) {
         // since otherwise there is a noticeable lag
         message_edit_countdown_timer.text(timer_text(seconds_left));
         var countdown_timer = setInterval(function () {
-            if (seconds_left - 1 <= 0) {
+            seconds_left -= 1;
+            if (seconds_left <= 0) {
                 clearInterval(countdown_timer);
                 message_edit_content.prop("readonly", "readonly");
                 if (message.type === 'stream') {