diff --git a/tools/datafiles.py b/tools/datafiles.py
index 35da69a..d87fc08 100644
--- a/tools/datafiles.py
+++ b/tools/datafiles.py
@@ -39,4 +39,4 @@ class JSONFile(DataFile):
 
     def save(self):
         with open(self.filename, "wt") as f:
-            f.write(json.dumps(self.copy()))
+            f.write(json.dumps(self.copy(), indent=4))