diff --git a/raiden/api/python.py b/raiden/api/python.py
index 4bddd2e57e..bd3c41d0d3 100644
--- a/raiden/api/python.py
+++ b/raiden/api/python.py
@@ -755,8 +755,11 @@ def transfer_async(
         if secret is not None and not isinstance(secret, typing.T_Secret):
             raise InvalidSecret("secret is not valid.")
 
-        if secrethash is not None and not isinstance(secrethash, typing.T_SecretHash):
-            raise InvalidSecretHash("secrethash is not valid.")
+        if secrethash is not None:
+            if not isinstance(secrethash, typing.T_SecretHash):
+                raise InvalidSecretHash("secrethash is not valid.")
+            if current_state.payment_mapping.secrethashes_to_task.get(secrethash):
+                raise InvalidSecretHash("task with the same secrethash is still pending")
 
         log.debug(
             "Initiating transfer",
diff --git a/raiden/transfer/mediated_transfer/initiator.py b/raiden/transfer/mediated_transfer/initiator.py
index 9ae488c737..cbe5f564a2 100644
--- a/raiden/transfer/mediated_transfer/initiator.py
+++ b/raiden/transfer/mediated_transfer/initiator.py
@@ -319,7 +319,19 @@ def handle_secretrequest(
 
     elif not is_valid_secretrequest and is_message_from_target:
         initiator_state.received_secret_request = True
-        iteration = TransitionResult(initiator_state, list())
+
+        if initiator_state.transfer_description.secret == EMPTY_SECRET:
+            transfer_description = initiator_state.transfer_description
+            payment_failed = EventPaymentSentFailed(
+                payment_network_address=transfer_description.payment_network_address,
+                token_network_address=transfer_description.token_network_address,
+                identifier=transfer_description.payment_identifier,
+                target=transfer_description.target,
+                reason="Target requested the secret but secret is unknown to the Initiator",
+            )
+            iteration = TransitionResult(initiator_state, [payment_failed])
+        else:
+            iteration = TransitionResult(initiator_state, list())
 
     else:
         iteration = TransitionResult(initiator_state, list())