diff --git a/nib/std/trivial.nix b/nib/std/trivial.nix
index cf26fb3..cb50a53 100644
--- a/nib/std/trivial.nix
+++ b/nib/std/trivial.nix
@@ -1,4 +1,9 @@
-{...}: {
+{...}: let
+  inherit
+    (builtins)
+    warn
+    ;
+in {
   id = x: x;
 
   min = x: y:
@@ -10,4 +15,9 @@
     if x > y
     then x
     else y;
+
+  warnIf = cond: msg:
+    if cond
+    then warn msg
+    else x: x;
 }