diff --git a/chainqueue/cache/base.py b/chainqueue/cache/base.py
index d94fe0f..ad7541c 100644
--- a/chainqueue/cache/base.py
+++ b/chainqueue/cache/base.py
@@ -33,6 +33,7 @@ class CacheTx:
         self.tx_index = None
         self.timestamp = None
 
+        self.src = None
         self.chain_spec = chain_spec