diff --git a/pkgs/misc/screensavers/slock/default.nix b/pkgs/misc/screensavers/slock/default.nix
index 55765a520da..6b310236de4 100644
--- a/pkgs/misc/screensavers/slock/default.nix
+++ b/pkgs/misc/screensavers/slock/default.nix
@@ -17,7 +17,7 @@ stdenv.mkDerivation rec {
 
   installFlags = "DESTDIR=\${out} PREFIX=";
 
-  patchPhase = "sed -i '/chmod u+s/d' Makefile";
+  postPatch = "sed -i '/chmod u+s/d' Makefile";
 
   preBuild = optionalString (conf != null) ''
     cp ${writeText "config.def.h" conf} config.def.h
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 4df368a51ed..2b05d1d345c 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -19104,7 +19104,9 @@ with pkgs;
 
   seafile-shared = callPackage ../misc/seafile-shared { };
 
-  slock = callPackage ../misc/screensavers/slock { };
+  slock = callPackage ../misc/screensavers/slock {
+    conf = config.slock.conf or null;
+  };
 
   smokeping = callPackage ../tools/networking/smokeping {
     inherit fping rrdtool;