diff --git a/ipynb/Portmantout.ipynb b/ipynb/Portmantout.ipynb
index b31b766..b08d0a0 100644
--- a/ipynb/Portmantout.ipynb
+++ b/ipynb/Portmantout.ipynb
@@ -719,7 +719,9 @@
     "\n",
     "def missing_bridges(W: Wordset) -> list[str]:\n",
     "    \"\"\"What 1-letter-suffix to 1-letter-prefix bridges are missing from W.bridges?\"\"\"\n",
-    "    return [A + B for (A, B) in letter_pairs if B not in W.bridges[A]]"
+    "    return [A + B for (A, B) in letter_pairs if B not in W.bridges[A]]\n",
+    "\n",
+    "assert not missing_bridges(W)"
    ]
   },
   {