diff --git a/apps/alarm/alarm.js b/apps/alarm/alarm.js
index db98cc4a0..28261110a 100644
--- a/apps/alarm/alarm.js
+++ b/apps/alarm/alarm.js
@@ -24,11 +24,11 @@ function showAlarm(alarm) {
   }).then(function(sleep) {
     buzzCount = 0;
     if (sleep) {
-      if(!alarm.ohr) alarm.ohr = alarm.hr;
+      if(alarm.ohr===undefined) alarm.ohr = alarm.hr;
       alarm.hr += 10/60; // 10 minutes
     } else {
       alarm.last = (new Date()).getDate();
-      if (alarm.ohr) {
+      if (alarm.ohr!==undefined) {
           alarm.hr = alarm.ohr;
           delete alarm.ohr;
       }