diff --git a/README.md b/README.md
index f2144de..3fd1484 100644
--- a/README.md
+++ b/README.md
@@ -100,13 +100,21 @@ eachSystem allSystems (system: { hello = 42; })
     flake-utils.lib.eachDefaultSystem (system:
       let pkgs = nixpkgs.legacyPackages.${system}; in
       {
-        packages = rec {
-          hello = pkgs.hello;
-          default = hello;
+        packages = {
+          default = pkgs.hello;
+          # `nix run .#find` will work because findutils.meta.mainProgram is set to "find".
+          find = pkgs.findutils;
         };
-        apps = rec {
-          hello = flake-utils.lib.mkApp { drv = self.packages.${system}.hello; };
-          default = hello;
+        # Use apps to expose packages that have multiple binaries.
+        apps = {
+          xargs = flake-utils.lib.mkApp {
+            drv = pkgs.findutils;
+            name = "xargs";
+          };
+          ls = flake-utils.lib.mkApp {
+            drv = pkgs.coreutils;
+            name = "ls";
+          };
         };
       }
     );
@@ -119,9 +127,16 @@ Meld merges subflakes using common inputs.  Useful when you want to
 split up a large flake with many different components into more
 manageable parts.
 
-### `mkApp { drv, name ? drv.pname or drv.name, exePath ? drv.passthru.exePath or "/bin/${name}"`
+### `mkApp { drv, name ? drv.pname or drv.name, exePath ? "/bin/${name}"`
 
-A small utility that builds the structure expected by the special `apps` and `defaultApp` prefixes.
+> **DEPRECATED**
+>
+> `mkApp` used to look for `drv.passthru.exePath`, and it's no longer the case.
+>
+> For derivations that only expose a single binary, set the `meta.mainProgram`
+> attribute on the package and expose it in the `packages`.
+
+A small utility that builds the structure expected by the special `apps` prefix.
 
 
 ### `flattenTree :: attrs -> attrs`
diff --git a/examples/each-system/flake.nix b/examples/each-system/flake.nix
index 7eff847..54f19b9 100644
--- a/examples/each-system/flake.nix
+++ b/examples/each-system/flake.nix
@@ -7,13 +7,21 @@
     flake-utils.lib.eachDefaultSystem (system:
       let pkgs = nixpkgs.legacyPackages.${system}; in
       {
-        packages = rec {
-          hello = pkgs.hello;
-          default = hello;
+        packages = {
+          default = pkgs.hello;
+          # `nix run .#find` will work because findutils.meta.mainProgram is set to "find".
+          find = pkgs.findutils;
         };
-        apps = rec {
-          hello = flake-utils.lib.mkApp { drv = self.packages.${system}.hello; };
-          default = hello;
+        # Use apps to expose packages that have multiple binaries.
+        apps = {
+          xargs = flake-utils.lib.mkApp {
+            drv = pkgs.findutils;
+            name = "xargs";
+          };
+          ls = flake-utils.lib.mkApp {
+            drv = pkgs.coreutils;
+            name = "ls";
+          };
         };
       }
     );
diff --git a/lib.nix b/lib.nix
index a774f18..9f1b915 100644
--- a/lib.nix
+++ b/lib.nix
@@ -202,11 +202,23 @@ let
     recursiveUpdate output (import subflake inputs)) { };
 
   # Returns the structure used by `nix app`
-  mkApp =
+  mkApp = let
+    # Pulled from nixpkgs.lib
+    warn =
+      if builtins.elem (builtins.getEnv "NIX_ABORT_ON_WARN") ["1" "true" "yes"]
+      then msg: builtins.trace "warning: ${msg}" (abort "NIX_ABORT_ON_WARN=true; warnings are treated as unrecoverable errors.")
+      else msg: builtins.trace "warning: ${msg}";
+  in
     { drv
     , name ? drv.pname or drv.name
-    , exePath ? drv.passthru.exePath or "/bin/${name}"
+    , exePath ? "/bin/${name}"
     }:
+    (if (drv.passthru or {}) ? exePath then
+    warn
+      "flake-utils.lib.mkApp: ${name} has the deprecated `drv.passthru.exePath` attribute. Please pass the `exePath` directly."
+    else
+      lib.id
+    )
     {
       type = "app";
       program = "${drv}${exePath}";