diff --git a/app/src/main/java/com/todoroo/astrid/alarms/AlarmService.kt b/app/src/main/java/com/todoroo/astrid/alarms/AlarmService.kt
index f45178ed7..f7564684a 100644
--- a/app/src/main/java/com/todoroo/astrid/alarms/AlarmService.kt
+++ b/app/src/main/java/com/todoroo/astrid/alarms/AlarmService.kt
@@ -24,10 +24,9 @@ class AlarmService @Inject constructor(
         private val alarmDao: AlarmDao,
         private val jobs: NotificationQueue) {
 
-    // TODO: remove runBlocking
-    fun rescheduleAlarms(taskId: Long, oldDueDate: Long, newDueDate: Long) = runBlocking {
-        if (newDueDate <= 0 || newDueDate <= oldDueDate) {
-            return@runBlocking
+    suspend fun rescheduleAlarms(taskId: Long, oldDueDate: Long, newDueDate: Long) {
+        if (oldDueDate <= 0 || newDueDate <= 0 || newDueDate <= oldDueDate) {
+            return
         }
         val alarms: MutableSet<Long> = LinkedHashSet()
         for (alarm in getAlarms(taskId)) {
diff --git a/app/src/main/java/com/todoroo/astrid/repeats/RepeatTaskHelper.kt b/app/src/main/java/com/todoroo/astrid/repeats/RepeatTaskHelper.kt
index fe5b46e4a..385bccd52 100644
--- a/app/src/main/java/com/todoroo/astrid/repeats/RepeatTaskHelper.kt
+++ b/app/src/main/java/com/todoroo/astrid/repeats/RepeatTaskHelper.kt
@@ -63,7 +63,13 @@ class RepeatTaskHelper @Inject constructor(
             task.setDueDateAdjustingHideUntil(newDueDate)
             gcalHelper.rescheduleRepeatingTask(task)
             taskDao.save(task)
-            alarmService.rescheduleAlarms(task.id, oldDueDate, newDueDate)
+            alarmService.rescheduleAlarms(
+                    task.id,
+                    oldDueDate
+                            .takeIf { it > 0 }
+                    // try to guess original due date when no due date was set
+                            ?: newDueDate - (computeNextDueDate(task, recurrence, repeatAfterCompletion) - newDueDate),
+                    newDueDate)
             localBroadcastManager.broadcastRepeat(task.id, oldDueDate, newDueDate)
         }
     }