diff --git a/artiq/gateware/test/drtio/test_full_stack.py b/artiq/gateware/test/drtio/test_full_stack.py
index 61fb43d2a..e55bb536a 100644
--- a/artiq/gateware/test/drtio/test_full_stack.py
+++ b/artiq/gateware/test/drtio/test_full_stack.py
@@ -303,7 +303,7 @@ class TestFullStack(unittest.TestCase):
                 yield
             yield dut.master.rt_packet.echo_stb.eq(0)
 
-            for i in range(15):
+            for i in range(17):
                 yield
 
             self.assertEqual((yield dut.master.rt_packet.packet_cnt_tx), 1)