diff --git a/lib/modules.nix b/lib/modules.nix
index bb16acac7e24..13844feb303f 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -1167,7 +1167,7 @@ let
       if isDefined then
         if type.merge ? v2 then
           # check and merge share the same closure
-          # .headError is either non-present null or an error describing string
+          # .headError is either not-present, null, or a string describing the error
           if checkedAndMerged.headError or null != null then
             throw "A definition for option `${showOption loc}' is not of type `${type.description}'. TypeError: ${checkedAndMerged.headError.message}"
           else