diff --git a/lib/spack/spack/cmd/install.py b/lib/spack/spack/cmd/install.py
index 79af35d3a0d..de45c7ca4fc 100644
--- a/lib/spack/spack/cmd/install.py
+++ b/lib/spack/spack/cmd/install.py
@@ -47,7 +47,7 @@ def setup_parser(subparser):
         '--only',
         default='package,dependencies',
         dest='things_to_install',
-        choices=['package', 'dependencies', 'package,dependencies'],
+        choices=['package', 'dependencies'],
         help="""Select the mode of installation.
 The default is to install the package along with all its dependencies.
 Alternatively one can decide to install only the package or only