diff --git a/src/test/wpt/run.sh b/src/test/wpt/run.sh
index 5a6a71ffc51..1d05280d0db 100755
--- a/src/test/wpt/run.sh
+++ b/src/test/wpt/run.sh
@@ -19,4 +19,5 @@ fi
 python $servo_root/src/test/wpt/run.py \
   --config $servo_root/src/test/wpt/config.ini \
   --binary $objdir/../servo \
+  --log-mach - \
   "$@"