diff --git a/libraries/chain/protocol/transaction.cpp b/libraries/chain/protocol/transaction.cpp
index 49854a1e..21fd9c8e 100644
--- a/libraries/chain/protocol/transaction.cpp
+++ b/libraries/chain/protocol/transaction.cpp
@@ -111,7 +111,7 @@ struct sign_state
        *  Checks to see if we have signatures of the active authorites of
        *  the accounts specified in authority or the keys specified. 
        */
-      bool check_authority( const authority* au, int depth = 0 )
+      bool check_authority( const authority* au, uint32_t depth = 0 )
       {
          if( au == nullptr ) return false;
          const authority& auth = *au;