diff --git a/changelog.d/16153.bugfix b/changelog.d/16153.bugfix
new file mode 100644
index 000000000000..2fcc74736a93
--- /dev/null
+++ b/changelog.d/16153.bugfix
@@ -0,0 +1,3 @@
+Checking authdict dictionary before accessing session from it.
+
+Contributed by @prajjawal05
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 59ecafa6a094..e2fc9299710b 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -483,7 +483,7 @@ async def check_ui_auth(
 
         sid: Optional[str] = None
         authdict = clientdict.pop("auth", {})
-        if "session" in authdict:
+        if authdict and "session" in authdict:
             sid = authdict["session"]
 
         # Convert the URI and method to strings.