diff --git a/builder/build-package b/builder/build-package
index e89df96..de81629 100755
--- a/builder/build-package
+++ b/builder/build-package
@@ -13,8 +13,17 @@ detect_package_format() {
   fi
 }
 
+warn_build_tag_not_supported_for_rpm_and_exit() {
+  if [[ "$package_format" = "rpm" ]]; then
+    echo >&2 "<build_tag> isn't supported for rpm"
+    exit 1
+  fi
+}
+
 cd "$(dirname "$0")/.."
 
 detect_package_format
+warn_build_tag_not_supported_for_rpm_and_exit
+
 builder/build-tarball "$os" "$codename" "$build_tag"
 builder/build-${package_format} "$os" "$codename" "$build_tag"
diff --git a/builder/build-rpm b/builder/build-rpm
index 39724d5..f3fdf2d 100755
--- a/builder/build-rpm
+++ b/builder/build-rpm
@@ -2,8 +2,18 @@
 
 set -e
 
+warn_build_tag_not_supported_for_rpm_and_exit() {
+  local build_tag="$1"
+
+  if [[ -n "$build_tag" ]]; then
+    echo >&2 "<build_tag> isn't supported for rpm"
+    exit 1
+  fi
+}
+
 cd "$(dirname "$0")/.."
 . builder/os_ver_cli.sh
+warn_build_tag_not_supported_for_rpm_and_exit "$build_tag"
 
 docker build -t kasmvnc_rpmbuilder_${os}:${os_codename} -f \
   builder/dockerfile.${os}_${os_codename}.rpm.build .