diff --git a/lib/spack/spack/config.py b/lib/spack/spack/config.py
index 982b730f16..f58c331edb 100644
--- a/lib/spack/spack/config.py
+++ b/lib/spack/spack/config.py
@@ -107,7 +107,7 @@
 
 #: metavar to use for commands that accept scopes
 #: this is shorter and more readable than listing all choices
-SCOPES_METAVAR = "{defaults,system,site,user}[/PLATFORM] or env:ENVIRONMENT"
+SCOPES_METAVAR = "{defaults,system,site,user,command_line}[/PLATFORM] or env:ENVIRONMENT"
 
 #: Base name for the (internal) overrides scope.
 _OVERRIDES_BASE_NAME = "overrides-"