diff --git a/mpcontribs-api/mpcontribs/api/notebooks/views.py b/mpcontribs-api/mpcontribs/api/notebooks/views.py
index 38bc51ab2..ec83b4109 100644
--- a/mpcontribs-api/mpcontribs/api/notebooks/views.py
+++ b/mpcontribs-api/mpcontribs/api/notebooks/views.py
@@ -110,7 +110,7 @@ def build():
 
 def restart_kernels():
     """use to avoid run-away memory"""
-    kernel_ids = [k for k, v in current_app.kernels.items() if v["cid"] is None]
+    kernel_ids = [k for k, v in current_app.kernels.items() if v is None]
 
     for kernel_id in kernel_ids:
         kernel_url = get_kernel_endpoint(kernel_id) + "/restart"