diff --git a/nixos/modules/services/logging/logcheck.nix b/nixos/modules/services/logging/logcheck.nix
index 6069262b4705..3a85fa60fe7a 100644
--- a/nixos/modules/services/logging/logcheck.nix
+++ b/nixos/modules/services/logging/logcheck.nix
@@ -11,7 +11,10 @@ let
                    rm $out/logcheck.*
                  '';
 
-  rulesDir = pkgs.symlinkJoin "logcheck-rules-dir" ([ defaultRules ] ++ cfg.extraRulesDirs);
+  rulesDir = pkgs.symlinkJoin
+    { name = "logcheck-rules-dir";
+      paths = ([ defaultRules ] ++ cfg.extraRulesDirs);
+    };
 
   configFile = pkgs.writeText "logcheck.conf" cfg.config;
 
diff --git a/nixos/modules/services/mail/dovecot.nix b/nixos/modules/services/mail/dovecot.nix
index 127c3da69d14..47e374d8edc3 100644
--- a/nixos/modules/services/mail/dovecot.nix
+++ b/nixos/modules/services/mail/dovecot.nix
@@ -63,8 +63,10 @@ let
     cfg.extraConfig
   ];
 
-  modulesDir = pkgs.symlinkJoin "dovecot-modules"
-    (map (pkg: "${pkg}/lib/dovecot") ([ dovecotPkg ] ++ map (module: module.override { dovecot = dovecotPkg; }) cfg.modules));
+  modulesDir = pkgs.symlinkJoin {
+    name = "dovecot-modules";
+    paths = map (pkg: "${pkg}/lib/dovecot") ([ dovecotPkg ] ++ map (module: module.override { dovecot = dovecotPkg; }) cfg.modules);
+  };
 
 in
 {
diff --git a/pkgs/build-support/trivial-builders.nix b/pkgs/build-support/trivial-builders.nix
index fef91e1d89dc..b0040cf18177 100644
--- a/pkgs/build-support/trivial-builders.nix
+++ b/pkgs/build-support/trivial-builders.nix
@@ -47,16 +47,24 @@ rec {
 
 
   # Create a forest of symlinks to the files in `paths'.
-  symlinkJoin = name: paths:
+  symlinkJoin =
+    { name
+    , paths
+    , preferLocalBuild ? true
+    , allowSubstitutes ? false
+    , postBuild ? ""
+    , buildInputs ? []
+    , meta ? {}
+    }:
     runCommand name
-      { inherit paths;
-        preferLocalBuild = true; allowSubstitutes = false;
+      { inherit paths preferLocalBuild allowSubstitutes buildInputs meta;
       }
       ''
         mkdir -p $out
         for i in $paths; do
           ${lndir}/bin/lndir $i $out
         done
+        ${postBuild}
       '';
 
 
diff --git a/pkgs/desktops/kde-5/plasma-5.5/default.nix b/pkgs/desktops/kde-5/plasma-5.5/default.nix
index a4f5c7c23204..3921f93a41d1 100644
--- a/pkgs/desktops/kde-5/plasma-5.5/default.nix
+++ b/pkgs/desktops/kde-5/plasma-5.5/default.nix
@@ -51,8 +51,10 @@ let
       let
         version = (builtins.parseDrvName breeze-qt5.name).version;
       in
-        symlinkJoin "breeze-${version}"
-        (map (pkg: pkg.out or pkg) [ breeze-gtk breeze-qt4 breeze-qt5 ]);
+        symlinkJoin {
+          name = "breeze-${version}";
+          paths = map (pkg: pkg.out or pkg) [ breeze-gtk breeze-qt4 breeze-qt5 ];
+        };
     kde-cli-tools = callPackage ./kde-cli-tools.nix {};
     kde-gtk-config = callPackage ./kde-gtk-config {};
     kdecoration = callPackage ./kdecoration.nix {};