diff --git a/src/pycookiecheat/firefox.py b/src/pycookiecheat/firefox.py
index ae68454..483e69a 100644
--- a/src/pycookiecheat/firefox.py
+++ b/src/pycookiecheat/firefox.py
@@ -75,10 +75,7 @@ def _get_profiles_dir_for_os(
         raise ValueError(
             f"OS must be one of {list(FIREFOX_OS_PROFILE_DIRS.keys())}"
         )
-    try:
-        return Path(os_config[browser]).expanduser()
-    except KeyError:
-        raise ValueError(f"Browser must be one of {list(os_config.keys())}")
+    return Path(os_config[browser]).expanduser()
 
 
 def _find_firefox_default_profile(firefox_dir: Path) -> str:
diff --git a/tests/test_firefox.py b/tests/test_firefox.py
index af4379c..f8578ba 100644
--- a/tests/test_firefox.py
+++ b/tests/test_firefox.py
@@ -262,8 +262,10 @@ def test_get_profiles_dir_for_os_invalid() -> None:
     """Test invalid OS and browser names."""
     with pytest.raises(ValueError, match="OS must be one of"):
         _get_profiles_dir_for_os("invalid")
-    with pytest.raises(ValueError, match="Browser must be one of"):
-        _get_profiles_dir_for_os("linux", "invalid")  # type: ignore
+    with pytest.raises(
+        ValueError, match="'invalid' is not a valid BrowserType"
+    ):
+        _get_profiles_dir_for_os("linux", BrowserType("invalid"))
 
 
 # _find_firefox_default_profile()