diff --git a/src/c3nav/mapdata/packageio/read.py b/src/c3nav/mapdata/packageio/read.py
index d2145df4..3ddbeb34 100644
--- a/src/c3nav/mapdata/packageio/read.py
+++ b/src/c3nav/mapdata/packageio/read.py
@@ -44,7 +44,7 @@ def _read_folder(package, cls, path, check_sister_file=False):
     objects = []
     if not os.path.isdir(path):
         return []
-    for filename in os.listdir(path):
+    for filename in sorted(os.listdir(path)):
         if not filename.endswith('.json'):
             continue
 
diff --git a/src/c3nav/mapdata/packageio/write.py b/src/c3nav/mapdata/packageio/write.py
index cab9c305..9d4355a1 100644
--- a/src/c3nav/mapdata/packageio/write.py
+++ b/src/c3nav/mapdata/packageio/write.py
@@ -45,7 +45,7 @@ def _write_folder(objects, path, prettify=False, check_only=False, check_sister_
             count += _write_object(obj, path, filename, prettify, check_only)
 
     if os.path.isdir(full_path):
-        for filename in os.listdir(full_path):
+        for filename in sorted(os.listdir(full_path)):
             full_filename = os.path.join(full_path, filename)
             if filename in filenames or not filename.endswith('.json') or not os.path.isfile(full_filename):
                 continue