diff --git a/scripts/build-image.sh b/scripts/build-image.sh
index afeb7bd..49020c6 100755
--- a/scripts/build-image.sh
+++ b/scripts/build-image.sh
@@ -38,7 +38,7 @@ fi
 if [ -z "${GAMECI_OS}" ]; then
 
     # windows-il2cpp requires windows OS
-    if [ "${GAMECI_OS}" = "windows-il2cpp" ]; then
+    if [ "${UNITY_PLATFORM}" = "windows-il2cpp" ]; then
         GAMECI_OS="windows"
     else
         GAMECI_OS="ubuntu"