diff --git a/build/qemu-smoke.sh b/build/qemu-smoke.sh
index 64cc744..3ad81d9 100644
--- a/build/qemu-smoke.sh
+++ b/build/qemu-smoke.sh
@@ -128,7 +128,7 @@ fi
 
 cat > "$MNT_DIR/opt/run-smoke.sh" <<'SMOKE_EOF'
 #!/usr/bin/env bash
-set -euo pipefail
+set -uo pipefail
 
 PASS=0
 FAIL=0
@@ -138,10 +138,10 @@ check() {
   local name="$1"; shift
   if "$@" >/dev/null 2>&1; then
     RESULTS+=("PASS: $name")
-    ((PASS++))
+    PASS=$((PASS+1))
   else
     RESULTS+=("FAIL: $name")
-    ((FAIL++))
+    FAIL=$((FAIL+1))
   fi
 }