diff --git a/aleksis/core/mixins.py b/aleksis/core/mixins.py
index 299856da61c628cfae1fce91f1c1a3319c4d8af4..e44caa020bdb6fb1814a3b7e10de95d72915b26b 100644
--- a/aleksis/core/mixins.py
+++ b/aleksis/core/mixins.py
@@ -118,7 +118,7 @@ class ExtensibleModel(models.Model, metaclass=_ExtensibleModelBase):
         for i, version in enumerate(versions):
             diff = {}
             if i > 0:
-                prev_version = versions[i-1]
+                prev_version = versions[i - 1]
 
                 for k, val in version.field_dict.items():
                     prev_val = prev_version.field_dict.get(k, None)