diff --git a/pkgs/development/python-modules/generic/default.nix b/pkgs/development/python-modules/generic/default.nix
index 8da833b0dc1a..e007795105fc 100644
--- a/pkgs/development/python-modules/generic/default.nix
+++ b/pkgs/development/python-modules/generic/default.nix
@@ -37,6 +37,7 @@
       runHook postCheck
     ''
 
+, preInstall ? ""
 , postInstall ? ""
 
 , ... } @ attrs:
@@ -63,7 +64,7 @@ python.stdenv.mkDerivation (attrs // {
     ${preConfigure}
   '';
 
-  installPhase = ''
+  installPhase = preInstall + ''
     mkdir -p "$out/lib/${python.libPrefix}/site-packages"
 
     echo "installing \`${name}' with \`easy_install'..."
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index bc336a2c8029..41b545a68623 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -2599,7 +2599,6 @@ let pythonPackages = python.modules // rec {
           sha256 = "1wif9r6307qhlcp2zbg6n05yvxxn9ppkxh8gpsplcbyh22zi7bcd";
         };
 
-      preInstallPhases = "preInstall";
       preInstall = ''
         cp ${x_ignore_nofocus}/* .
         sed -i 's|dlopen(library,|dlopen("libX11.so.6",|' x_ignore_nofocus.c