diff --git a/frr-k8s-image/_service b/frr-k8s-image/_service
index 058ae16..99fc7e0 100644
--- a/frr-k8s-image/_service
+++ b/frr-k8s-image/_service
@@ -9,7 +9,7 @@
   </service>
   <service name="replace_using_env" mode="buildtime">
     <param name="file">Dockerfile</param>
-    <param name="eval">IMG_PREFIX=$(rpm --macros=/root/.rpmmacros -E %img_prefix)</param>
+    <param name="eval">IMG_PREFIX=$(rpm --macros=/root/.rpmmacros -E %{?img_prefix})</param>
     <param name="var">IMG_PREFIX</param>
     <param name="eval">IMG_REPO=$(rpm --macros=/root/.rpmmacros -E %img_repo)</param>
     <param name="var">IMG_REPO</param>