diff --git a/pkgs/applications/misc/spacefm/default.nix b/pkgs/applications/misc/spacefm/default.nix
index e1f98fceace..7dbe723d9eb 100644
--- a/pkgs/applications/misc/spacefm/default.nix
+++ b/pkgs/applications/misc/spacefm/default.nix
@@ -15,9 +15,9 @@ in stdenv.mkDerivation rec {
 
   buildInputs = [ gtk3 udev desktop_file_utils shared_mime_info intltool pkgconfig makeWrapper ];
 
-  postInstall = ''
+  preFixup = ''
     wrapProgram "$out/bin/spacefm" \
-      --prefix XDG_DATA_DIRS : "${gtk3}/share"
+      --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH"
   '';
 
   meta = {
diff --git a/pkgs/applications/networking/browsers/midori/default.nix b/pkgs/applications/networking/browsers/midori/default.nix
index db9e1c24cb5..d3135e0be8e 100644
--- a/pkgs/applications/networking/browsers/midori/default.nix
+++ b/pkgs/applications/networking/browsers/midori/default.nix
@@ -32,9 +32,9 @@ stdenv.mkDerivation rec {
     -DUSE_ZEITGEIST=OFF
   '';
 
-  postInstall = ''
+  preFixup = ''
     wrapProgram $out/bin/midori \
       --prefix GIO_EXTRA_MODULES : "${glib_networking}/lib/gio/modules" \
-      --prefix XDG_DATA_DIRS : "${gtk3}/share:${gsettings_desktop_schemas}/share"
+      --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH"
   '';
 }
diff --git a/pkgs/applications/networking/p2p/transmission-remote-gtk/default.nix b/pkgs/applications/networking/p2p/transmission-remote-gtk/default.nix
index 5403f6e3156..968aba20754 100644
--- a/pkgs/applications/networking/p2p/transmission-remote-gtk/default.nix
+++ b/pkgs/applications/networking/p2p/transmission-remote-gtk/default.nix
@@ -11,9 +11,9 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ makeWrapper pkgconfig intltool gtk3 json_glib curl ];
 
-  postInstall = ''
+  preFixup = ''
     wrapProgram "$out/bin/transmission-remote-gtk" \
-      --prefix XDG_DATA_DIRS : "${gtk3}/share"
+      --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH"
   '';
 
   meta = {
diff --git a/pkgs/applications/networking/p2p/transmission/default.nix b/pkgs/applications/networking/p2p/transmission/default.nix
index 958e19a0986..29fb558c83d 100644
--- a/pkgs/applications/networking/p2p/transmission/default.nix
+++ b/pkgs/applications/networking/p2p/transmission/default.nix
@@ -27,10 +27,10 @@ stdenv.mkDerivation rec {
   configureFlags = [ "--with-systemd-daemon" ]
     ++ optional enableGTK3 "--with-gtk";
 
-  postInstall = optionalString enableGTK3 /* gsettings schemas for file dialogues */ ''
+  preFixup = optionalString enableGTK3 /* gsettings schemas for file dialogues */ ''
     rm "$out/share/icons/hicolor/icon-theme.cache"
     wrapProgram "$out/bin/transmission-gtk" \
-      --prefix XDG_DATA_DIRS : "${gtk3}/share"
+      --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH"
   '';
 
   meta = with stdenv.lib; {
diff --git a/pkgs/applications/office/gnumeric/default.nix b/pkgs/applications/office/gnumeric/default.nix
index 0ae27e322b7..014aa5bf0fd 100644
--- a/pkgs/applications/office/gnumeric/default.nix
+++ b/pkgs/applications/office/gnumeric/default.nix
@@ -20,9 +20,12 @@ stdenv.mkDerivation rec {
     goffice gtk3 makeWrapper
   ];
 
-  postInstall = ''
-    wrapProgram "$out"/bin/gnumeric-* \
-      --prefix XDG_DATA_DIRS : "${gtk3}/share:${gnome_icon_theme}/share"
+  preFixup = ''
+    for f in "$out"/bin/gnumeric-*; do
+      wrapProgram $f \
+        --prefix XDG_DATA_DIRS : "$XDG_ICON_DIRS:$GSETTINGS_SCHEMAS_PATH"
+    done
+    rm $out/share/icons/hicolor/icon-theme.cache
   '';
 
   meta = with stdenv.lib; {
diff --git a/pkgs/applications/video/pitivi/default.nix b/pkgs/applications/video/pitivi/default.nix
index 947d2517808..7f53aa07db6 100644
--- a/pkgs/applications/video/pitivi/default.nix
+++ b/pkgs/applications/video/pitivi/default.nix
@@ -1,7 +1,7 @@
 { stdenv, fetchurl, pkgconfig, intltool, itstool, makeWrapper
 , pythonPackages, gst, clutter-gst, clutter-gtk
 , gobjectIntrospection, clutter, gtk3, librsvg
-, gnome_icon_theme, gnome_icon_theme_symbolic
+, gnome_icon_theme, gnome_icon_theme_symbolic, gnome3
 }:
 
 let
@@ -39,20 +39,18 @@ in stdenv.mkDerivation rec {
     python pygobject3 pyxdg numpy pycairo sqlite3
   ]);
 
-  postInstall = with stdenv.lib; with gst; let
+  preFixup = with stdenv.lib; with gst; let
     libraryPath = makeLibraryPath [
       gstreamer gst-editing-services
       clutter-gst clutter-gtk clutter gtk3
-    ];
-
-    xdgDataDirs = makeSearchPath "share" [
-      gtk3 gnome_icon_theme gnome_icon_theme_symbolic
+      gnome3.gnome_desktop
     ];
   in ''
     wrapProgram "$out/bin/pitivi" \
       --set GDK_PIXBUF_MODULE_FILE "$GDK_PIXBUF_MODULE_FILE" \
       --prefix LD_LIBRARY_PATH : "${libraryPath}" \
       --prefix GST_PLUGIN_SYSTEM_PATH_1_0 : "$GST_PLUGIN_SYSTEM_PATH_1_0" \
-      --prefix XDG_DATA_DIRS : "\$XDG_ICON_DIRS:${xdgDataDirs}:$out/share"
+      --prefix XDG_DATA_DIRS : "\$XDG_ICON_DIRS:$out/share:$GSETTINGS_SCHEMAS_PATH"
+    rm $out/share/icons/hicolor/icon-theme.cache
   '';
 }