diff --git a/heavy_script.sh b/heavy_script.sh
index a452cbd8..49786818 100644
--- a/heavy_script.sh
+++ b/heavy_script.sh
@@ -66,7 +66,7 @@ do
         eval nextopt=${!OPTIND}
         # existing or starting with dash?
         if [[ -n $nextopt && $nextopt != -* ]] ; then
-            OPTIND=$((OPTIND + 1))
+            OPTIND=$((OPTIND++))
             ignore+=("$nextopt")
         else
             echo "Option: \"-i\" requires an argument"