diff --git a/lib/Properties.hs b/lib/Properties.hs
index a4465d46df71c02215d20fa8b572497d42349150..27479980bc342867dceb5ea52f1ef219b96d2ec9 100644
--- a/lib/Properties.hs
+++ b/lib/Properties.hs
@@ -69,7 +69,7 @@ checkMap = do
     $ complain "The map's tile size must be 32 by 32 pixels."
 
   unlessHasProperty "mapCopyright"
-    $ error "must give the map's copyright via the \"mapCopyright\" property."
+    $ complain "must give the map's copyright via the \"mapCopyright\" property."
 
 -- | Checks a single property of a map.
 --
@@ -117,8 +117,8 @@ checkTileset = do
   when (isJust (tilesetSource tileset))
     $ complain "Tilesets must be embedded and cannot be loaded from external files."
   -- TODO: check copyright!
-  unlessHasProperty "tiledCopyright"
-    $ forbid "property \"tiledCopyright\" for tilesets must be set."
+  unlessHasProperty "tilesetCopyright"
+    $ forbid "property \"tilesetCopyright\" for tilesets must be set."
 
   -- check individual tileset properties
   mapM_ checkTilesetProperty (fromMaybe [] $ tilesetProperties tileset)