diff --git a/pkgs/misc/flashfocus/default.nix b/pkgs/misc/flashfocus/default.nix
index 8c7fb067f1ab..f49c7936f60e 100644
--- a/pkgs/misc/flashfocus/default.nix
+++ b/pkgs/misc/flashfocus/default.nix
@@ -1,4 +1,4 @@
-{ lib, python3Packages, fetchPypi, netcat-openbsd, nix-update-script }:
+{ lib, python3Packages, fetchPypi, netcat-openbsd, procps, bash, nix-update-script }:
 
 python3Packages.buildPythonApplication rec {
   pname = "flashfocus";
@@ -13,13 +13,20 @@ python3Packages.buildPythonApplication rec {
 
   postPatch = ''
     substituteInPlace bin/nc_flash_window \
-      --replace "nc" "${lib.getExe netcat-openbsd}"
+      --replace-fail "nc" "${lib.getExe netcat-openbsd}"
+
+    substituteInPlace src/flashfocus/util.py \
+      --replace-fail "pidof" "${lib.getExe' procps "pidof"}"
   '';
 
   nativeBuildInputs = with python3Packages; [
     setuptools
   ];
 
+  buildInputs = [
+    bash
+  ];
+
   pythonRelaxDeps = [
     "pyyaml"
     "xcffib"