diff --git a/install-mpsd-software-environment.py b/install-mpsd-software-environment.py
index b68e56f8f93d7a38f294e915a0a14ed040ed0dcd..2da318e9163f21e425ac161460eb25e045e4383c 100755
--- a/install-mpsd-software-environment.py
+++ b/install-mpsd-software-environment.py
@@ -300,8 +300,10 @@ def main():
             subp.add_argument("release", type=str, help="Release version to install or remove")
             if cmd in ["install", "reinstall"]:
                 subp.add_argument(
-                    "--toolchain",
-                    "--toolchains",
+                    "--toolchains", # first option defines attribute
+                                    # name `args.toolchains` in `args = parser_args()`
+                    "--toolchain",  # allow singular as alternative 
+                                    # (-> creates attribute `args.toolchains` if used)
                     type=str,
                     nargs="+",
                     default="NONE",