diff --git a/lib/trivial.nix b/lib/trivial.nix
index fcd9a8791dcf..fd48a0456b66 100644
--- a/lib/trivial.nix
+++ b/lib/trivial.nix
@@ -1101,11 +1101,10 @@ in
     ```
   */
   functionArgs =
-    f:
-    if f ? __functor then
-      f.__functionArgs or (functionArgs (f.__functor f))
-    else
-      builtins.functionArgs f;
+    let
+      functionArgs = builtins.functionArgs;
+    in
+    f: if f ? __functor then f.__functionArgs or (functionArgs (f.__functor f)) else functionArgs f;
 
   /**
     Check whether something is a function or something
@@ -1123,7 +1122,11 @@ in
     isFunction : Any -> Bool
     ```
   */
-  isFunction = f: builtins.isFunction f || (f ? __functor && isFunction (f.__functor f));
+  isFunction =
+    let
+      isFunction = builtins.isFunction;
+    in
+    f: isFunction f || (f ? __functor && isFunction (f.__functor f));
 
   /**
     `mirrorFunctionArgs f g` creates a new function `g'` with the same behavior as `g` (`g' x == g x`)