diff --git a/plenum/server/pool_req_handler.py b/plenum/server/pool_req_handler.py
index <HASH>..<HASH> 100644
--- a/plenum/server/pool_req_handler.py
+++ b/plenum/server/pool_req_handler.py
@@ -25,7 +25,7 @@ class PoolRequestHandler(RequestHandler):
         self.state = state
         self.domainState = domainState
 
-    def validate(self, req: Request):
+    def validate(self, req: Request, config = None):
         typ = req.operation.get(TXN_TYPE)
         error = None
         if typ == NODE:
diff --git a/plenum/server/req_handler.py b/plenum/server/req_handler.py
index <HASH>..<HASH> 100644
--- a/plenum/server/req_handler.py
+++ b/plenum/server/req_handler.py
@@ -19,7 +19,7 @@ class RequestHandler:
         self.ledger = ledger
         self.state = state
 
-    def validate(self, req: Request, config):
+    def validate(self, req: Request, config = None):
         pass
 
     def applyReq(self, req: Request):
add config=None argument to validate method to make sub and super signatures match