diff --git a/x-pack/test/alerting_api_integration/basic/tests/actions/builtin_action_types/slack.ts b/x-pack/test/alerting_api_integration/basic/tests/actions/builtin_action_types/slack.ts
index 0c16c08b91a10..7161276f2c63a 100644
--- a/x-pack/test/alerting_api_integration/basic/tests/actions/builtin_action_types/slack.ts
+++ b/x-pack/test/alerting_api_integration/basic/tests/actions/builtin_action_types/slack.ts
@@ -41,5 +41,9 @@ export default function slackTest({ getService }: FtrProviderContext) {
             'Action type .slack is disabled because your basic license does not support it. Please upgrade your license.',
         });
     });
+
+    after(() => {
+      slackServer.close();
+    });
   });
 }
diff --git a/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/builtin_action_types/slack.ts b/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/builtin_action_types/slack.ts
index 88801cd0d1cad..aa09a7e0d66ff 100644
--- a/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/builtin_action_types/slack.ts
+++ b/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/builtin_action_types/slack.ts
@@ -217,5 +217,9 @@ export default function slackTest({ getService }: FtrProviderContext) {
       expect(result.message).to.match(/error posting a slack message, retry later/);
       expect(result.retry).to.equal(true);
     });
+
+    after(() => {
+      slackServer.close();
+    });
   });
 }