diff --git a/client/src/__locales/en.json b/client/src/__locales/en.json
index 9fc65cac6d0..15f28c87a43 100644
--- a/client/src/__locales/en.json
+++ b/client/src/__locales/en.json
@@ -222,6 +222,7 @@
     "updated_upstream_dns_toast": "Upstream servers successfully saved",
     "dns_test_ok_toast": "Specified DNS servers are working correctly",
     "dns_test_not_ok_toast": "Server \"{{key}}\": could not be used, please check that you've written it correctly",
+    "dns_test_warning_toast": "Server \"{{key}}\": doesn't respond for the test request and thus may not work properly",
     "unblock": "Unblock",
     "block": "Block",
     "disallow_this_client": "Disallow this client",
diff --git a/client/src/actions/index.js b/client/src/actions/index.js
index 8e153224c11..e1b4e96c38a 100644
--- a/client/src/actions/index.js
+++ b/client/src/actions/index.js
@@ -314,13 +314,15 @@ export const testUpstream = (
         const testMessages = Object.keys(upstreamResponse)
             .map((key) => {
                 const message = upstreamResponse[key];
-                if (message !== 'OK') {
+                if (message.startsWith('WARNING:')) {
+                    dispatch(addErrorToast({ error: i18next.t('dns_test_warning_toast', { key }) }));
+                } else if (message !== 'OK') {
                     dispatch(addErrorToast({ error: i18next.t('dns_test_not_ok_toast', { key }) }));
                 }
                 return message;
             });
 
-        if (testMessages.every((message) => message === 'OK')) {
+        if (testMessages.every((message) => message === 'OK' || message.startsWith('WARNING:'))) {
             dispatch(addSuccessToast('dns_test_ok_toast'));
         }