diff --git a/tests/unit/forklift/test_legacy.py b/tests/unit/forklift/test_legacy.py
index 577fb8473d0b..812ad8e27c5c 100644
--- a/tests/unit/forklift/test_legacy.py
+++ b/tests/unit/forklift/test_legacy.py
@@ -919,7 +919,6 @@ def test_fails_with_invalid_names(self, pyramid_config, db_request, name):
             "for more information."
         ).format(name)
 
-    @pytest.mark.xfail(reason="https://github.com/pypa/warehouse/issues/4079")
     @pytest.mark.parametrize(
         ("description_content_type", "description", "message"),
         [
diff --git a/warehouse/forklift/legacy.py b/warehouse/forklift/legacy.py
index 171d8b85a05c..fa8456769be7 100644
--- a/warehouse/forklift/legacy.py
+++ b/warehouse/forklift/legacy.py
@@ -934,33 +934,32 @@ def file_upload(request):
     rendered = None
     if form.description.data:
         description_content_type = form.description_content_type.data
-        # if not description_content_type:
-        #     description_content_type = "text/x-rst"
+        if not description_content_type:
+            description_content_type = "text/x-rst"
+
         rendered = readme.render(
-            form.description.data, description_content_type  # use_fallback=False
+            form.description.data, description_content_type, use_fallback=False
         )
 
         # Uploading should prevent broken rendered descriptions.
-        # Temporarily disabled, see
-        # https://github.com/pypa/warehouse/issues/4079
-        # if rendered is None:
-        #     if form.description_content_type.data:
-        #         message = (
-        #             "The description failed to render "
-        #             "for '{description_content_type}'."
-        #         ).format(description_content_type=description_content_type)
-        #     else:
-        #         message = (
-        #             "The description failed to render "
-        #             "in the default format of reStructuredText."
-        #         )
-        #     raise _exc_with_message(
-        #         HTTPBadRequest,
-        #         "{message} See {projecthelp} for more information.".format(
-        #             message=message,
-        #             projecthelp=request.help_url(_anchor="description-content-type"),
-        #         ),
-        #     ) from None
+        if rendered is None:
+            if form.description_content_type.data:
+                message = (
+                    "The description failed to render "
+                    "for '{description_content_type}'."
+                ).format(description_content_type=description_content_type)
+            else:
+                message = (
+                    "The description failed to render "
+                    "in the default format of reStructuredText."
+                )
+            raise _exc_with_message(
+                HTTPBadRequest,
+                "{message} See {projecthelp} for more information.".format(
+                    message=message,
+                    projecthelp=request.help_url(_anchor="description-content-type"),
+                ),
+            ) from None
 
     try:
         canonical_version = packaging.utils.canonicalize_version(form.version.data)