diff --git a/tests/test_spawner.py b/tests/test_spawner.py
index 9daa7cdc..6a64f923 100644
--- a/tests/test_spawner.py
+++ b/tests/test_spawner.py
@@ -1,4 +1,5 @@
 import asyncio
+import base64
 import json
 import os
 from functools import partial
@@ -365,6 +366,32 @@ async def test_spawn_component_label(
     await spawner.stop()
 
 
+async def test_spawner_internal_ssl_secret(
+    ssl_app,
+    config,
+):
+    spawner = KubeSpawner(
+        config=config,
+        # hub=hub_ssl,
+        user=MockUser(name="ssl"),
+        # api_token="abc123",
+        # oauth_client_id="unused",
+        internal_ssl=True,
+        internal_trust_bundles=ssl_app.internal_trust_bundles,
+        internal_certs_location=ssl_app.internal_certs_location,
+        _mock=True,
+    )
+    # initialize ssl config
+    hub_paths = await spawner.create_certs()
+
+    spawner.cert_paths = await spawner.move_certs(hub_paths)
+
+    # Validate that certificates were correctly encoded as base64
+    manifest = spawner.get_secret_manifest(None)
+    for _, secret in manifest.data.items():
+        base64.b64decode(secret, validate=True)
+
+
 async def test_spawn_internal_ssl(
     kube_ns,
     kube_client,