diff --git a/micropip/_utils.py b/micropip/_utils.py
index 9d6bc35..1167a01 100644
--- a/micropip/_utils.py
+++ b/micropip/_utils.py
@@ -142,9 +142,9 @@ def check_compatible(filename: str) -> None:
     try:
         tags = parse_tags(filename)
     except InvalidWheelFilename:
-        raise ValueError(f"Wheel filename is invalid: {filename}") from None
+        raise ValueError(f"Wheel filename is invalid: {filename!r}") from None
     except InvalidVersion:
-        raise ValueError(f"Wheel version is invalid: {filename}") from None
+        raise ValueError(f"Wheel version is invalid: {filename!r}") from None
 
     tag: Tag = next(iter(tags))
     if "emscripten" not in tag.platform:
diff --git a/micropip/wheelinfo.py b/micropip/wheelinfo.py
index c6d255f..d9c5a89 100644
--- a/micropip/wheelinfo.py
+++ b/micropip/wheelinfo.py
@@ -54,6 +54,9 @@ class WheelInfo:
     _dist_info: Path | None = None
 
     def __post_init__(self):
+        assert (
+            self.url.startwith(p) for p in ("http:", "https:", "emfs:", "file:")
+        ), self.url
         self._project_name = safe_name(self.name)
 
     @classmethod
@@ -63,6 +66,8 @@ def from_url(cls, url: str) -> "WheelInfo":
         See https://www.python.org/dev/peps/pep-0427/#file-name-convention
         """
         parsed_url = urlparse(url)
+        if parsed_url.scheme == "":
+            url = "file:///" + url
         file_name = Path(parsed_url.path).name
         name, version, build, tags = parse_wheel_filename(file_name)
         return WheelInfo(
diff --git a/tests/conftest.py b/tests/conftest.py
index af55b88..c704a57 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -270,7 +270,7 @@ def add_pkg_version(
         releases[version] = [
             {
                 "filename": filename,
-                "url": filename,
+                "url": f"http://fake.domain/f/{filename}",
                 "digests": {
                     "sha256": Wildcard(),
                 },
diff --git a/tests/test_install.py b/tests/test_install.py
index 111926a..aa89b0e 100644
--- a/tests/test_install.py
+++ b/tests/test_install.py
@@ -257,7 +257,7 @@ def _mock_fetch_bytes(arg, *args, **kwargs):
 
     msg = "Access-Control-Allow-Origin"
     with pytest.raises(ValueError, match=msg):
-        await micropip.install("htps://x.com/xxx-1.0.0-py3-none-any.whl")
+        await micropip.install("https://x.com/xxx-1.0.0-py3-none-any.whl")
 
 
 @pytest.mark.skip_refcount_check
diff --git a/tests/test_transaction.py b/tests/test_transaction.py
index 326490d..78b81d3 100644
--- a/tests/test_transaction.py
+++ b/tests/test_transaction.py
@@ -7,17 +7,21 @@
     "path",
     [
         SNOWBALL_WHEEL,
-        f"/{SNOWBALL_WHEEL}" f"a/{SNOWBALL_WHEEL}",
+        f"/{SNOWBALL_WHEEL}",
+        f"a/{SNOWBALL_WHEEL}",
         f"/a/{SNOWBALL_WHEEL}",
         f"//a/{SNOWBALL_WHEEL}",
     ],
 )
-@pytest.mark.parametrize("protocol", ["https:", "file:", "emfs:", ""])
+@pytest.mark.parametrize(
+    "protocol",
+    ["http:", "https:", "file:", "emfs:", ""],
+)
 def test_parse_wheel_url1(protocol, path):
     pytest.importorskip("packaging")
     from micropip.transaction import WheelInfo
 
-    url = protocol + path
+    url = protocol + path if protocol else "file:///" + path
     wheel = WheelInfo.from_url(url)
     assert wheel.name == "snowballstemmer"
     assert str(wheel.version) == "2.0.0"