diff --git a/rad/views.py b/rad/views.py
index 2ac1bd86..c5146ad1 100644
--- a/rad/views.py
+++ b/rad/views.py
@@ -686,7 +686,10 @@ def stats(request):
 
 # HTTP Error 400
 def page_not_found(request, exception):
-    response = render(request, "404.html")
+    # Provide the exception message (reason) to the template so callers
+    # can show a user-friendly explanation when available.
+    context = {"reason": str(exception) if exception is not None else "Not found"}
+    response = render(request, "404.html", context=context)
 
     response.status_code = 404