diff --git a/src/Lean/Language/Lean.lean b/src/Lean/Language/Lean.lean
index ab3beca6cbe5..ab8d27d7e402 100644
--- a/src/Lean/Language/Lean.lean
+++ b/src/Lean/Language/Lean.lean
@@ -315,7 +315,7 @@ def reparseOptions (opts : Options) : IO Options := do
       | unless weak do
           throw <| .userError s!"invalid -D parameter, unknown configuration option '{name}'
 
-If the option is defined in this library, use '-D{`weak ++ name}' to set it conditionally"
+If the option is defined in a library, use '-D{`weak ++ name}' to set it conditionally"
 
     let .ofString val := val
       | opts' := opts'.insert name val  -- Already parsed