diff --git a/artiq/gateware/test/rtio/test_sed_lane_distributor.py b/artiq/gateware/test/rtio/test_sed_lane_distributor.py
index 6c9135c86..7d4440a5c 100644
--- a/artiq/gateware/test/rtio/test_sed_lane_distributor.py
+++ b/artiq/gateware/test/rtio/test_sed_lane_distributor.py
@@ -14,6 +14,7 @@ def simulate(input_events, compensation=None, wait=True):
     if compensation is None:
         compensation = [0]*256
     dut = lane_distributor.LaneDistributor(LANE_COUNT, 8, layout, compensation, 3)
+    dut.comb += dut.enable_spread.eq(1)
 
     output = []
     access_results = []