diff --git a/templates/common/build_icon.sh b/templates/common/build_icon.sh
index 571c0dd388fb6d43268ed3fcad919936e8253fe8..12687f1cb059764a1848510d3845688eda042764 100644
--- a/templates/common/build_icon.sh
+++ b/templates/common/build_icon.sh
@@ -15,12 +15,14 @@ cd ${WORKDIR}
 load_spack "%spack.init%" "%spack.root%" "%spack.url%" "%spack.branch%" "%spack.compiler%" "%spack.disable_local_config%" "%spack.user_cache_path%"
 
 SPACK_BUILD_ICON="%icon.spack_cmd%"
-if [ ! -z $SPACK_BUILD_ICON ]; then
+if [ ! -z "$SPACK_BUILD_ICON" ]; then
   echo "Installing ICON with spack!"
   echo "cmd=$SPACK_BUILD_ICON"
   spack repo add ${WORKDIR}/proj/spack_repo
   spack install $SPACK_BUILD_ICON
   spack load $SPACK_BUILD_ICON
+else
+  echo "%icon.spack_cmd% is not defined. If you want to compile icon with spack, please provide a spack compile instruction string in your proj.yaml"
 fi
 
 # Need to get ECCODES DWD definitions: