diff --git a/scripts/smoke-test.sh b/scripts/smoke-test.sh
index d7e8dad..cb62e23 100755
--- a/scripts/smoke-test.sh
+++ b/scripts/smoke-test.sh
@@ -22,9 +22,9 @@ SIZE_THRESHOLD_MB=2200
 run() {
   local label="$1"; local cmd="$2"
   if docker run --rm --entrypoint="" "$IMAGE" sh -c "$cmd" >/dev/null 2>&1; then
-    printf "  ✅  %s\n" "$label"; ((PASS++))
+    printf "  ✅  %s\n" "$label"; PASS=$((PASS+1))
   else
-    printf "  ❌  %s\n" "$label"; ((FAIL++))
+    printf "  ❌  %s\n" "$label"; FAIL=$((FAIL+1))
   fi
 }
 
@@ -65,9 +65,9 @@ done
 exec_test() {
   local label="$1"; local cmd="$2"
   if docker exec "$CID" sh -c "$cmd" >/dev/null 2>&1; then
-    printf "  ✅  %s\n" "$label"; ((PASS++))
+    printf "  ✅  %s\n" "$label"; PASS=$((PASS+1))
   else
-    printf "  ❌  %s\n" "$label"; ((FAIL++))
+    printf "  ❌  %s\n" "$label"; FAIL=$((FAIL+1))
   fi
 }
 
@@ -81,9 +81,9 @@ echo ""
 echo "── Image size ──"
 SIZE_MB=$(docker image inspect "$IMAGE" --format='{{.Size}}' | awk '{printf "%d", $1/1048576}')
 if [ "$SIZE_MB" -le "$SIZE_THRESHOLD_MB" ]; then
-  printf "  ✅  size: %d MB (threshold %d MB)\n" "$SIZE_MB" "$SIZE_THRESHOLD_MB"; ((PASS++))
+  printf "  ✅  size: %d MB (threshold %d MB)\n" "$SIZE_MB" "$SIZE_THRESHOLD_MB"; PASS=$((PASS+1))
 else
-  printf "  ❌  size: %d MB exceeds threshold %d MB\n" "$SIZE_MB" "$SIZE_THRESHOLD_MB"; ((FAIL++))
+  printf "  ❌  size: %d MB exceeds threshold %d MB\n" "$SIZE_MB" "$SIZE_THRESHOLD_MB"; FAIL=$((FAIL+1))
 fi
 
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