diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 2f0c468..492a7de 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -574,8 +574,6 @@ struct CmdFlakeCheck : FlakeCommand
                                     *attr.value, *attr.pos);
                         }
 
-                        else
-                            warn("unknown flake output '%s'", name);
 
                     } catch (Error & e) {
                         e.addTrace(pos, hintfmt("while checking flake output '%s'", name));