diff --git a/Lib/packaging/metadata.py b/Lib/packaging/metadata.py
index 2d0ffa4..2993ebb 100644
--- a/Lib/packaging/metadata.py
+++ b/Lib/packaging/metadata.py
@@ -229,8 +229,10 @@
 
     def __delitem__(self, name):
         field_name = self._convert_name(name)
-        # we let a KeyError propagate
-        del self._fields[field_name]
+        try:
+            del self._fields[field_name]
+        except KeyError:
+            raise KeyError(name)
         self._set_best_version()
 
     def __contains__(self, name):