diff --git a/beetsplug/lastgenre/__init__.py b/beetsplug/lastgenre/__init__.py
index 573fd6dca..f14dcaa00 100644
--- a/beetsplug/lastgenre/__init__.py
+++ b/beetsplug/lastgenre/__init__.py
@@ -303,9 +303,7 @@ class LastGenrePlugin(plugins.BeetsPlugin):
         else:
             genre_str = obj.get("genre")
 
-        return [
-            g.lower() for g in genre_str.split(self.config["separator"].get())
-        ]
+        return genre_str.split(self.config["separator"].get())
 
     def _combine_genres(
         self, old: list[str], new: list[str]
@@ -346,10 +344,11 @@ class LastGenrePlugin(plugins.BeetsPlugin):
             return obj.get("genre"), "keep any, no-force"
 
         if self.config["force"]:
+            genres = self._get_existing_genres(obj)
             # Force doesn't keep any unless keep_existing is set.
             # Whitelist validation is handled in _resolve_genres.
             if self.config["keep_existing"]:
-                keep_genres = self._get_existing_genres(obj)
+                keep_genres = [g.lower() for g in genres]
 
         # Run through stages: track, album, artist,
         # album artist, or most popular track genre.