diff --git a/pony/orm/asttranslation.py b/pony/orm/asttranslation.py
index 6c9068b60..e818e2d1f 100644
--- a/pony/orm/asttranslation.py
+++ b/pony/orm/asttranslation.py
@@ -362,12 +362,25 @@ def create_extractors(code_key, tree, globals, locals, special_functions, const_
         for node in pretranslator.externals:
             src = node.src = ast2src(node)
             if src == '.0':
-                def extractor(globals, locals):
-                    return locals['.0']
+                extractor = Extractor('.0')
             else:
                 code = compile(src, src, 'eval')
-                def extractor(globals, locals, code=code):
-                    return eval(code, globals, locals)
+                extractor = Extractor(src, code)
             extractors[src] = extractor
         result = extractors_cache[code_key] = tree, extractors
     return result
+
+
+class Extractor(object):
+
+    def __init__(self, src, code=None):
+        self.src = src
+        self.code = code
+
+    def __call__(self, globals, locals):
+        if self.src == '.0':
+            return locals['.0']
+        return eval(self.code, globals, locals)
+
+    def __repr__(self):
+        return 'Extractor(%s)' % self.src