diff --git a/openage/assets.py b/openage/assets.py
index 8ffb06e484..ea8ca57830 100644
--- a/openage/assets.py
+++ b/openage/assets.py
@@ -18,10 +18,10 @@
 from . import default_dirs
 
 if typing.TYPE_CHECKING:
-    from openage.util.fslike.directory import Directory
+    from openage.util.fslike.union import UnionPath
 
 
-def get_asset_path(custom_asset_dir: str = None) -> Directory:
+def get_asset_path(custom_asset_dir: str = None) -> UnionPath:
     """
     Returns a Path object for the game assets.
 
@@ -33,13 +33,15 @@ def get_asset_path(custom_asset_dir: str = None) -> Directory:
     the game as its data source(s).
     """
 
+    # mount the possible locations in an union:
+    result = Union().root
+
     # if we're in devmode, use only the in-repo asset folder
     if not custom_asset_dir and config.DEVMODE:
-        return Directory(os.path.join(config.BUILD_SRC_DIR, "assets")).root
+        result.mount(Directory(os.path.join(config.BUILD_SRC_DIR, "assets")).root)
+        return result
 
-    # else, mount the possible locations in an union:
-    # overlay the global dir and the user dir.
-    result = Union().root
+    # else overlay the global dir and the user dir.
 
     # the cmake-determined folder for storing assets
     global_data = Path(config.GLOBAL_ASSET_DIR)
diff --git a/openage/convert/main.py b/openage/convert/main.py
index d9461eaeec..b66d99b73e 100644
--- a/openage/convert/main.py
+++ b/openage/convert/main.py
@@ -23,11 +23,12 @@
 if typing.TYPE_CHECKING:
     from argparse import ArgumentParser, Namespace
     from openage.util.fslike.directory import Directory
+    from openage.util.fslike.union import UnionPath
     from openage.util.fslike.path import Path
 
 
 def convert_assets(
-    assets: Directory,
+    assets: UnionPath,
     args: Namespace,
     srcdir: Directory = None
 ) -> None:
diff --git a/openage/convert/service/init/api_export_required.py b/openage/convert/service/init/api_export_required.py
index fe677ec246..61b8f5ba4d 100644
--- a/openage/convert/service/init/api_export_required.py
+++ b/openage/convert/service/init/api_export_required.py
@@ -13,17 +13,21 @@
 from .modpack_search import get_modpack_info
 
 if typing.TYPE_CHECKING:
-    from openage.util.fslike.directory import Directory
+    from openage.util.fslike.union import UnionPath
 
 
 CURRENT_API_VERSION = "0.4.0"
 
 
-def api_export_required(asset_dir: Directory) -> bool:
+def api_export_required(asset_dir: UnionPath) -> bool:
     """
     Returns true if the openage nyan API modpack cannot be found.
 
     TODO: Remove once the API modpack is generated by default.
+
+    :param asset_dir: The asset directory to search in.
+    :type asset_dir: UnionPath
+    :returns: True if the openage nyan API modpack cannot be found, else False.
     """
     modpack_dir = asset_dir / "converted" / "engine"
 
diff --git a/openage/convert/service/init/conversion_required.py b/openage/convert/service/init/conversion_required.py
index 0c09b4ea67..1c13a33142 100644
--- a/openage/convert/service/init/conversion_required.py
+++ b/openage/convert/service/init/conversion_required.py
@@ -11,10 +11,10 @@
 from .modpack_search import enumerate_modpacks
 
 if typing.TYPE_CHECKING:
-    from openage.util.fslike.directory import Directory
+    from openage.util.fslike.union import UnionPath
 
 
-def conversion_required(asset_dir: Directory) -> bool:
+def conversion_required(asset_dir: UnionPath) -> bool:
     """
     Check if an asset conversion is required to run the game.
 
@@ -24,7 +24,7 @@ def conversion_required(asset_dir: Directory) -> bool:
         - the converted assets are outdated
 
     :param asset_dir: The asset directory to check.
-    :type asset_dir: Directory
+    :type asset_dir: UnionPath
     :return: True if an asset conversion is required, else False.
     """
     try:
diff --git a/openage/convert/service/init/modpack_search.py b/openage/convert/service/init/modpack_search.py
index 986d25be2b..ea8bf87c24 100644
--- a/openage/convert/service/init/modpack_search.py
+++ b/openage/convert/service/init/modpack_search.py
@@ -11,15 +11,15 @@
 from ....log import info, dbg
 
 if typing.TYPE_CHECKING:
-    from openage.util.fslike.directory import Directory
+    from openage.util.fslike.union import UnionPath
 
 
-def enumerate_modpacks(modpacks_dir: Directory) -> set[str]:
+def enumerate_modpacks(modpacks_dir: UnionPath) -> set[str]:
     """
     Enumerate openage modpacks in a directory.
 
     :param asset_dir: The asset directory to search in.
-    :type asset_dir: Directory
+    :type asset_dir: UnionPath
     :returns: A list of modpack names that were found.
     :rtype: set[str]
     """
@@ -42,12 +42,12 @@ def enumerate_modpacks(modpacks_dir: Directory) -> set[str]:
     return modpacks
 
 
-def get_modpack_info(modpack_dir: Directory) -> dict[str, typing.Any]:
+def get_modpack_info(modpack_dir: UnionPath) -> dict[str, typing.Any]:
     """
     Get information about an openage modpack from its definition file.
 
     :param modpack_dir: Modpack root directory.
-    :type modpack_dir: Directory
+    :type modpack_dir: UnionPath
     :returns: Modpack information.
     :rtype: dict[str, typing.Any]
 
@@ -56,7 +56,7 @@ def get_modpack_info(modpack_dir: Directory) -> dict[str, typing.Any]:
     :raises toml.TomlDecodeError: If the modpack definition file is malformed.
     """
     if not modpack_dir.exists():
-        info("Modpack directory %s not found", modpack_dir.root.name)
+        info("Modpack directory %s not found", modpack_dir.name)
         raise FileNotFoundError("Modpack directory not found")
 
     modpack_def = modpack_dir / "modpack.toml"
@@ -68,7 +68,7 @@ def get_modpack_info(modpack_dir: Directory) -> dict[str, typing.Any]:
         return content
 
     except FileNotFoundError as err:
-        dbg("Modpack definition file not found; ncould not find %s", modpack_def)
+        dbg("Modpack definition file not found; could not find %s", modpack_def)
         raise err
 
     except TypeError as err: