diff --git a/pkgs/build-support/mkshell/default.nix b/pkgs/build-support/mkshell/default.nix
index 69897459088..a70dc0390cb 100644
--- a/pkgs/build-support/mkshell/default.nix
+++ b/pkgs/build-support/mkshell/default.nix
@@ -11,13 +11,8 @@
   ...
 }@attrs:
 let
-  mergeInputs = name:
-    let
-      op = item: sum: sum ++ item."${name}" or [];
-      nul = [];
-      list = [attrs] ++ inputsFrom;
-    in
-      lib.foldr op nul list;
+  mergeInputs = name: lib.concatLists (lib.catAttrs name
+    ([attrs] ++ inputsFrom));
 
   rest = builtins.removeAttrs attrs [
     "inputsFrom"