diff --git a/test/functional/interface_zmq.py b/test/functional/interface_zmq.py
index 4c23c4d30c1..527126fac38 100755
--- a/test/functional/interface_zmq.py
+++ b/test/functional/interface_zmq.py
@@ -27,7 +27,7 @@ def hash256_reversed(byte_str):
 
 class ZMQSubscriber:
     def __init__(self, socket, topic):
-        self.sequence = 0
+        self.sequence = None  # no sequence number received yet
         self.socket = socket
         self.topic = topic
 
@@ -39,7 +39,11 @@ class ZMQSubscriber:
         # Topic should match the subscriber topic.
         assert_equal(topic, self.topic)
         # Sequence should be incremental.
-        assert_equal(struct.unpack('<I', seq)[-1], self.sequence)
+        received_seq = struct.unpack('<I', seq)[-1]
+        if self.sequence is None:
+            self.sequence = received_seq
+        else:
+            assert_equal(received_seq, self.sequence)
         self.sequence += 1
         return body