diff --git a/twine/package.py b/twine/package.py
index 0845105b..5018d370 100644
--- a/twine/package.py
+++ b/twine/package.py
@@ -73,12 +73,21 @@ def _safe_name(name: str) -> str:
     return re.sub("[^A-Za-z0-9.]+", "-", name)
 
 
+class CheckedDistribution(pkginfo.Distribution):
+    """
+    A Distribution whose name and version are confirmed to be defined.
+    """
+
+    name: str
+    version: str
+
+
 class PackageFile:
     def __init__(
         self,
         filename: str,
         comment: Optional[str],
-        metadata: pkginfo.Distribution,
+        metadata: CheckedDistribution,
         python_version: Optional[str],
         filetype: Optional[str],
     ) -> None:
@@ -88,7 +97,7 @@ def __init__(
         self.metadata = metadata
         self.python_version = python_version
         self.filetype = filetype
-        self.safe_name = _safe_name(cast(str, metadata.name))
+        self.safe_name = _safe_name(metadata.name)
         self.signed_filename = self.filename + ".asc"
         self.signed_basefilename = self.basefilename + ".asc"
         self.gpg_signature: Optional[Tuple[str, bytes]] = None
@@ -156,7 +165,9 @@ def from_filename(cls, filename: str, comment: Optional[str]) -> "PackageFile":
         else:
             py_version = None
 
-        return cls(filename, comment, meta, py_version, dtype)
+        return cls(
+            filename, comment, cast(CheckedDistribution, meta), py_version, dtype
+        )
 
     @staticmethod
     def _is_unknown_metadata_version(
diff --git a/twine/repository.py b/twine/repository.py
index 32c54702..5b2e288e 100644
--- a/twine/repository.py
+++ b/twine/repository.py
@@ -142,7 +142,10 @@ def _upload(self, package: package_file.PackageFile) -> requests.Response:
 
         with open(package.filename, "rb") as fp:
             data_to_send.append(
-                ("content", (package.basefilename, fp, "application/octet-stream"))
+                (
+                    "content",
+                    (package.basefilename, fp, "application/octet-stream"),
+                )
             )
             encoder = requests_toolbelt.MultipartEncoder(data_to_send)
 
@@ -223,7 +226,7 @@ def package_is_uploaded(
                 releases = {}
             self._releases_json_data[safe_name] = releases
 
-        packages = releases.get(cast(str, package.metadata.version), [])
+        packages = releases.get(package.metadata.version, [])
 
         for uploaded_package in packages:
             if uploaded_package["filename"] == package.basefilename: