diff --git a/IPython/core/extensions.py b/IPython/core/extensions.py
index 6bf2048..b537393 100644
--- a/IPython/core/extensions.py
+++ b/IPython/core/extensions.py
@@ -151,4 +151,4 @@ class ExtensionManager(Configurable):
             raise ValueError("The file must have a .py or .zip extension", filename)
         
         filename = os.path.join(self.ipython_extension_dir, filename)
-        return urlretrieve(url, filename)
+        return copy(url, filename)