diff --git a/bypy/linux/__main__.py b/bypy/linux/__main__.py
index e4de56325f..55494f4fe8 100644
--- a/bypy/linux/__main__.py
+++ b/bypy/linux/__main__.py
@@ -15,10 +15,7 @@ from functools import partial
 from bypy.constants import (
     OUTPUT_DIR, PREFIX, SRC as CALIBRE_DIR, is64bit, python_major_minor_version
 )
-from bypy.freeze import (
-    extract_extension_modules, freeze_python, path_to_freeze_dir,
-    save_importer_src_to_header
-)
+from bypy.freeze import extract_extension_modules, freeze_python, path_to_freeze_dir
 from bypy.utils import (
     create_job, get_dll_path, mkdtemp, parallel_build, py_compile, run, walk
 )
@@ -170,9 +167,8 @@ def copy_python(env, ext_dir):
     print('Extracting extension modules from', env.py_dir, 'to', pdir)
     ext_map.update(extract_extension_modules(env.py_dir, pdir))
     py_compile(env.py_dir)
-    freeze_python(env.py_dir, pdir, env.obj_dir)
+    freeze_python(env.py_dir, pdir, env.obj_dir, ext_map, develop_mode_env_var='CALIBRE_DEVELOP_FROM')
     shutil.rmtree(env.py_dir)
-    save_importer_src_to_header(env.obj_dir, ext_map, develop_mode_env_var='CALIBRE_DEVELOP_FROM')
 
 
 def build_launchers(env):
diff --git a/bypy/macos/__main__.py b/bypy/macos/__main__.py
index 7df491552c..0613daa58f 100644
--- a/bypy/macos/__main__.py
+++ b/bypy/macos/__main__.py
@@ -22,10 +22,7 @@ from itertools import repeat
 from bypy.constants import (
     OUTPUT_DIR, PREFIX, PYTHON, SRC as CALIBRE_DIR, python_major_minor_version
 )
-from bypy.freeze import (
-    extract_extension_modules, freeze_python, path_to_freeze_dir,
-    save_importer_src_to_header
-)
+from bypy.freeze import extract_extension_modules, freeze_python, path_to_freeze_dir
 from bypy.utils import current_dir, mkdtemp, py_compile, timeit, walk
 
 abspath, join, basename, dirname = os.path.abspath, os.path.join, os.path.basename, os.path.dirname
@@ -648,9 +645,8 @@ class Freeze(object):
             os.rename(join(src, x), join(pydir, x))
         os.rmdir(src)
         py_compile(pydir)
-        freeze_python(pydir, dest, self.inc_dir)
+        freeze_python(pydir, dest, self.inc_dir, self.ext_map, develop_mode_env_var='CALIBRE_DEVELOP_FROM')
         shutil.rmtree(pydir)
-        save_importer_src_to_header(self.inc_dir, self.ext_map, develop_mode_env_var='CALIBRE_DEVELOP_FROM')
 
     def create_app_clone(self, name, specialise_plist, remove_doc_types=False, base_dir=None):
         print('\nCreating ' + name)
diff --git a/bypy/windows/__main__.py b/bypy/windows/__main__.py
index 4da42ef990..1d9b72fa7b 100644
--- a/bypy/windows/__main__.py
+++ b/bypy/windows/__main__.py
@@ -21,7 +21,7 @@ from bypy.constants import (
 )
 from bypy.freeze import (
     cleanup_site_packages, extract_extension_modules, freeze_python,
-    path_to_freeze_dir, save_importer_src_to_header
+    path_to_freeze_dir
 )
 from bypy.utils import mkdtemp, py_compile, run, walk
 
@@ -213,9 +213,8 @@ def freeze(env, ext_dir, incdir):
     py_compile(env.lib_dir.replace(os.sep, '/'))
     # from bypy.utils import run_shell
     # run_shell(cwd=env.lib_dir)
-    freeze_python(env.lib_dir, env.dll_dir, incdir)
+    freeze_python(env.lib_dir, env.dll_dir, incdir, ext_map, develop_mode_env_var='CALIBRE_DEVELOP_FROM')
     shutil.rmtree(env.lib_dir)
-    save_importer_src_to_header(incdir, ext_map, develop_mode_env_var='CALIBRE_DEVELOP_FROM')
 
 
 def embed_manifests(env):