diff --git a/src/calibre/debug.py b/src/calibre/debug.py
index 7814af5d9d..b8f89c7e11 100644
--- a/src/calibre/debug.py
+++ b/src/calibre/debug.py
@@ -278,6 +278,9 @@ def main(args=sys.argv):
                 inspect_mobi(path)
             else:
                 print ('Cannot dump unknown filetype: %s' % path)
+    elif len(args) >= 2 and os.path.exists(os.path.join(args[1], '__main__.py')):
+        sys.path.insert(0, args[1])
+        run_script(os.path.join(args[1], '__main__.py'), args[2:])
     else:
         from calibre import ipython
         ipython()