diff --git a/lib/Properties.hs b/lib/Properties.hs
index b586c7ea9a07d0711e188c2555d41c504ea6b5f5..35c4ce45fedc249d055061c3491daaceb96f3e91 100644
--- a/lib/Properties.hs
+++ b/lib/Properties.hs
@@ -428,8 +428,21 @@ checkTileThing removeExits p@(Property name _value) = case name of
         forbidEmptyLayer
         unwrapURI (Proxy @"map") p
           (\link -> do
-              dependsOn (MapLink link)
-              setProperty "exitUrl" link
+              assemblyslug <- lintConfig configAssemblyTag
+              case T.stripPrefix ("/@/rc3_21/"<>assemblyslug<>"/") link of
+                Nothing -> do
+                  dependsOn (MapLink link)
+                  setProperty "exitUrl" link
+                Just path -> case parsePath path of
+                  OkRelPath (Path _ p frag) -> do
+                    up <- askFileDepth
+                    dependsOn (LocalMap (Path up p frag))
+                    setProperty "exitUrl" path
+                    warn "You should use relative links to your own assembly instead \
+                         \of world://-style links (I've tried to adjust them \
+                         \automatically for now)."
+                  _ -> complain "There's a path I don't understand here. Perhaps try \
+                                \asking a human?"
           )
           $ \path ->
             let ext = getExtension path in