diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
index b91538b..de03d81 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
@@ -82,7 +82,10 @@
 import {GrButton} from '../../shared/gr-button/gr-button';
 import {GrLabelScores} from '../gr-label-scores/gr-label-scores';
 import {GrLabelScoreRow} from '../gr-label-score-row/gr-label-score-row';
-import {PolymerDeepPropertyChange} from '@polymer/polymer/interfaces';
+import {
+  PolymerDeepPropertyChange,
+  PolymerSpliceChange,
+} from '@polymer/polymer/interfaces';
 import {
   areSetsEqual,
   assertIsDefined,
@@ -499,6 +502,16 @@
     return selectorEl?.selectedValue;
   }
 
+  @observe('_reviewers.splices', '_ccs.splices')
+  reviewerOrCCChanged(
+    reviewerSplices?: PolymerSpliceChange<AccountInfo[] | GroupInfo[]>,
+    ccsSplices?: PolymerSpliceChange<AccountInfo[] | GroupInfo[]>
+  ) {
+    if (reviewerSplices?.indexSplices || ccsSplices?.indexSplices) {
+      this._reviewersMutated = true;
+    }
+  }
+
   accountAdded(e: CustomEvent<AccountInputDetail>) {
     const account = e.detail.account;
     const key = accountOrGroupKey(account);
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.ts b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.ts
index e324cf2d..1c0768e 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog_test.ts
@@ -1697,6 +1697,8 @@
       mutations.push(...review.reviewers!);
     });
 
+    assert.isFalse(element._reviewersMutated);
+
     // Remove and add to other field.
     reviewers.dispatchEvent(
       new CustomEvent('remove', {
@@ -1705,6 +1707,9 @@
         bubbles: true,
       })
     );
+
+    assert.isTrue(element._reviewersMutated);
+
     ccs.$.entry.dispatchEvent(
       new CustomEvent('add', {
         detail: {value: {account: reviewer1}},