diff --git a/run/serial.sh b/run/serial.sh
index 708b7ad..148178a 100644
--- a/run/serial.sh
+++ b/run/serial.sh
@@ -31,7 +31,7 @@ HOST_ARGS+=("-cpu_arch=${HOST_CPU}")
 [ -n "$HOST_VERSION" ] && HOST_ARGS+=("-version=${HOST_VERSION}")
 [ -n "$HOST_TIMESTAMP" ] && HOST_ARGS+=("-ts=${HOST_TIMESTAMP}")
 
-if [[ "${HOST_DEBUG}" == [Yy]* ]]; then
+if [[ "${HOST_DEBUG}" == [Yy1]* ]]; then
   set -x
   ./run/host.bin "${HOST_ARGS[@]}" &
   { set +x; } 2>/dev/null