diff --git a/client_code/routing/_navigation.py b/client_code/routing/_navigation.py
index d6e0411d..cdfef619 100644
--- a/client_code/routing/_navigation.py
+++ b/client_code/routing/_navigation.py
@@ -15,6 +15,8 @@
 
 # re-initialise the state object which was overridden on load or this is a new session
 state = history.state or {"url": location.hash, "pos": 0}
+if "url" not in state:
+    state = {"url": location.hash, "pos": 0}
 history.replaceState(state, "", state["url"])
 
 # undo and pos are used for unload behavior