diff --git a/src/ui/EditTask.svelte b/src/ui/EditTask.svelte
index d8f6e63279..d264655a9f 100644
--- a/src/ui/EditTask.svelte
+++ b/src/ui/EditTask.svelte
@@ -1,6 +1,7 @@
 <script lang="ts">
     import { onMount } from 'svelte';
     import { TASK_FORMATS, getSettings } from '../Config/Settings';
+    import { parseTypedDateForDisplayUsingFutureDate } from '../lib/DateTools';
     import type { Status } from '../Statuses/Status';
     import type { Task } from '../Task/Task';
     import DateEditor from './DateEditor.svelte';
@@ -99,6 +100,29 @@
     ];
 
     $: accesskey = (key: string) => (withAccessKeys ? key : null);
+
+    $: {
+        const cancelledAndDoneDateAreSet = editableTask.cancelledDate.length > 0 && editableTask.doneDate.length > 0;
+        if (cancelledAndDoneDateAreSet) {
+            isCancelledDateValid = false;
+            isDoneDateValid = false;
+        } else {
+            const cancelledParsedDate = parseTypedDateForDisplayUsingFutureDate(
+                'cancelled',
+                editableTask.cancelledDate,
+                editableTask.forwardOnly,
+            );
+            isCancelledDateValid = !cancelledParsedDate.includes('invalid');
+
+            const doneParsedDate = parseTypedDateForDisplayUsingFutureDate(
+                'done',
+                editableTask.doneDate,
+                editableTask.forwardOnly,
+            );
+            isDoneDateValid = !doneParsedDate.includes('invalid');
+        }
+    }
+
     $: formIsValid =
         isDueDateValid &&
         isRecurrenceValid &&