diff --git a/src/calibre/customize/builtins.py b/src/calibre/customize/builtins.py
index a60b69bf18..54f4e52f8c 100644
--- a/src/calibre/customize/builtins.py
+++ b/src/calibre/customize/builtins.py
@@ -1727,6 +1727,28 @@ plugins += [
 if __name__ == '__main__':
     # Test load speed
     import subprocess, textwrap
+    try:
+        subprocess.check_call(['python', '-c', textwrap.dedent(
+        '''
+        import init_calibre  # noqa
+
+        def doit():
+            import calibre.customize.builtins as b  # noqa
+
+        def show_stats():
+            from pstats import Stats
+            s = Stats('/tmp/calibre_stats')
+            s.sort_stats('cumulative')
+            s.print_stats(30)
+
+        import cProfile
+        cProfile.run('doit()', '/tmp/calibre_stats')
+        show_stats()
+
+        '''
+        )])
+    except subprocess.CalledProcessError:
+        raise SystemExit(1)
     try:
         subprocess.check_call(['python', '-c', textwrap.dedent(
         '''