diff --git a/common/verification.py b/common/verification.py
index 77394e7..f8861c6 100644
--- a/common/verification.py
+++ b/common/verification.py
@@ -28,6 +28,9 @@ def restore_field(data: dict) -> tuple:
             elif isinstance(v, bool):
                 sign_kv[key] = str(v).lower()
                 res[key] = int(v)
+            elif v is None:
+                sign_kv[key] = 'null'
+                res[key] = ''
             else:
                 sign_kv[key] = v
     return res, sign_kv