diff --git a/fsl/utils/filetree/filetree.py b/fsl/utils/filetree/filetree.py
index b1dad5f1b14c467e207ace2a518e977856880fe2..cbd8673dd79bd8a973990bd3ccab9f4a792e9b20 100644
--- a/fsl/utils/filetree/filetree.py
+++ b/fsl/utils/filetree/filetree.py
@@ -269,7 +269,7 @@ class FileTree(object):
             return obj
 
         with open(filename, 'w') as f:
-            json.dump(self, f, default=default)
+            json.dump(self, f, default=default, indent=2)
 
     @classmethod
     def load_pickle(cls, filename):