diff --git a/setup.py b/setup.py
index 6dee64febb0b3098bae1fdf6b7d2669981092c9c..902aab25bc94d700ca153113e06dabb2375a1287 100755
--- a/setup.py
+++ b/setup.py
@@ -1138,7 +1138,7 @@ def main():
 
     gi_ext = Extension(
         name='gi._gi',
-        sources=sources,
+        sources=sorted(sources),
         include_dirs=[script_dir, gi_dir],
         depends=list_headers(script_dir) + list_headers(gi_dir),
         define_macros=[("PY_SSIZE_T_CLEAN", None)],