Index: Lib/inspect.py
===================================================================
--- Lib/inspect.py	(revision 66810)
+++ Lib/inspect.py	(working copy)
@@ -521,7 +521,9 @@
     or code object.  The source code is returned as a list of all the lines
     in the file and the line number indexes a line in that list.  An IOError
     is raised if the source code cannot be retrieved."""
-    file = getsourcefile(object) or getfile(object)
+    file = getsourcefile(object)
+    if not file:
+        raise IOError('source code not available')
     module = getmodule(object, file)
     if module:
         lines = linecache.getlines(file, module.__dict__)