diff --git a/lib/modules/platform/gerrit/client.spec.ts b/lib/modules/platform/gerrit/client.spec.ts
index 8d64188c9f0fa3df546c2114a910832374613811..620ec9d5baef57cb54fff18c5e94a8ca161ca066 100644
--- a/lib/modules/platform/gerrit/client.spec.ts
+++ b/lib/modules/platform/gerrit/client.spec.ts
@@ -256,6 +256,18 @@ describe('modules/platform/gerrit/client', () => {
         .reply(200, gerritRestResponse([]), jsonResultHeader);
       await expect(client.addMessage(123456, 'message')).toResolve();
     });
+
+    it('add too big message', async () => {
+      const okMessage = 'a'.repeat(0x4000);
+      const tooBigMessage = okMessage + 'b';
+      httpMock
+        .scope(gerritEndpointUrl)
+        .post('/a/changes/123456/revisions/current/review', {
+          message: okMessage,
+        })
+        .reply(200, gerritRestResponse([]), jsonResultHeader);
+      await expect(client.addMessage(123456, tooBigMessage)).toResolve();
+    });
   });
 
   describe('checkForExistingMessage()', () => {
diff --git a/lib/modules/platform/gerrit/client.ts b/lib/modules/platform/gerrit/client.ts
index 4a5e3ccebab75c42507f99419559d0e41beac0f1..543328189ba7da37fffde1bfa53f8ca883bf8561 100644
--- a/lib/modules/platform/gerrit/client.ts
+++ b/lib/modules/platform/gerrit/client.ts
@@ -121,9 +121,10 @@ class GerritClient {
 
   async addMessage(
     changeNumber: number,
-    message: string,
+    fullMessage: string,
     tag?: string,
   ): Promise<void> {
+    const message = this.normalizeMessage(fullMessage);
     await this.gerritHttp.postJson(
       `a/changes/${changeNumber}/revisions/current/review`,
       { body: { message, tag } },
@@ -148,7 +149,7 @@ class GerritClient {
     message: string,
     tag?: string,
   ): Promise<void> {
-    const newMsg = message.trim(); //the last \n was removed from gerrit after the comment was added...
+    const newMsg = this.normalizeMessage(message);
     if (!(await this.checkForExistingMessage(changeNumber, newMsg, tag))) {
       await this.addMessage(changeNumber, newMsg, tag);
     }
@@ -213,6 +214,11 @@ class GerritClient {
     );
   }
 
+  normalizeMessage(message: string): string {
+    //the last \n was removed from gerrit after the comment was added...
+    return message.substring(0, 0x4000).trim();
+  }
+
   private static buildSearchFilters(
     repository: string,
     searchConfig: GerritFindPRConfig,