diff --git a/tools/gn/setup.cc b/tools/gn/setup.cc
index f3db362..ef26431 100644
--- a/tools/gn/setup.cc
+++ b/tools/gn/setup.cc
@@ -400,7 +400,7 @@
     OutputString(
         "\nThe build continued as if that argument was "
         "unspecified.\n\n");
-    return true;
+    // Nonfatal error.
   }
 
   if (check_public_headers_) {