diff --git a/tests/unit/cli/vyper_compile/test_compile_files.py b/tests/unit/cli/vyper_compile/test_compile_files.py
index 3856aa3362..528f7a42ae 100644
--- a/tests/unit/cli/vyper_compile/test_compile_files.py
+++ b/tests/unit/cli/vyper_compile/test_compile_files.py
@@ -424,4 +424,4 @@ def test_archive_search_path(tmp_path_factory, make_file, chdir_tmp_path):
         output_bundle = OutputBundle(compiler_data)
 
         used_dir = search_paths[-1].stem  # either dir1 or dir2
-        assert output_bundle.used_search_paths == [".", "0/" + used_dir]
+        assert output_bundle.used_search_paths == [".", str(Path("0", used_dir))]
diff --git a/vyper/cli/vyper_json.py b/vyper/cli/vyper_json.py
index 4f73732687..1478e188f6 100755
--- a/vyper/cli/vyper_json.py
+++ b/vyper/cli/vyper_json.py
@@ -235,7 +235,7 @@ def get_output_formats(input_dict: dict) -> dict[PurePath, list[str]]:
             output_paths = [PurePath(path) for path in input_dict["sources"].keys()]
         else:
             output_paths = [PurePath(path)]
-            if str(output_paths[0]) not in input_dict["sources"]:
+            if output_paths[0].as_posix() not in input_dict["sources"]:
                 raise JSONError(f"outputSelection references unknown contract '{output_paths[0]}'")
 
         for output_path in output_paths:
@@ -317,7 +317,7 @@ def compile_from_input_dict(
 def format_to_output_dict(compiler_data: dict) -> dict:
     output_dict: dict = {"compiler": f"vyper-{vyper.__version__}", "contracts": {}, "sources": {}}
     for path, data in compiler_data.items():
-        path = str(path)  # Path breaks json serializability
+        path = path.as_posix()
         output_dict["sources"][path] = {"id": data["source_id"]}
 
         for k in ("ast_dict", "annotated_ast_dict"):