diff --git a/core/views/survex.py b/core/views/survex.py
index a3f7f7c..8caa993 100644
--- a/core/views/survex.py
+++ b/core/views/survex.py
@@ -756,7 +756,7 @@ def survexcavesingle(request, cave_shortname):
     But might also be a link to a single survex file with no ".svx" suffix, which may not be a cave.
     
     If cave_shortname=="" then it used to list all caves which did not have a kataser number,
-    an accident of coding. This now does not happen.
+    an accident of coding. This now does not happen because urls.py has been changed to stop it.
     
     """
     if cave_shortname.startswith("caves-16"):
@@ -777,9 +777,14 @@ def survexcavesingle(request, cave_shortname):
                 # print(f"many {cave=} => {cave.sds=}")
             return render(request, "svxcaves.html", {"settings": settings, "caves": caves, "year": current_expo()})
         else:
-            # survex file not a cave, e.g. surface/1623/allsurface.svx
-            return svx(request, cave_shortname)
-            # return render(request, "errors/svxcaves404.html", {"settings": settings, "cave": cave_shortname, "year": current_expo()})
+            # A decision needs to be made: is this a silly thing or is it a real file?
+            filepath = settings.SURVEX_DATA / cave_shortname
+            if filepath.is_file():
+                print(filepath, type(filepath))
+                # survex file not a cave, e.g. surface/1623/allsurface.svx
+                return svx(request, cave_shortname)
+            else:
+                return render(request, "errors/svxcaves404.html", {"settings": settings, "cave": cave_shortname, "year": current_expo()})
 
 def check_cave_registered(areacode, survex_cave):
     """Checks whether a cave has been properly registered when it is found in the Loser repo