diff --git a/pkgs/development/libraries/qt-5/5.5/qtbase/default.nix b/pkgs/development/libraries/qt-5/5.5/qtbase/default.nix
index 7bfaafaf69ac..24e5ccb36f37 100644
--- a/pkgs/development/libraries/qt-5/5.5/qtbase/default.nix
+++ b/pkgs/development/libraries/qt-5/5.5/qtbase/default.nix
@@ -201,12 +201,11 @@ stdenv.mkDerivation {
 
   postInstall =
     ''
-      ${lib.optionalString buildDocs ''
-        make docs && make install_docs
-      ''}
-
       # Don't retain build-time dependencies like gdb and ruby.
       sed '/QMAKE_DEFAULT_.*DIRS/ d' -i $out/mkspecs/qconfig.pri
+    ''
+    + lib.optionalString buildDocs ''
+      make docs && make install_docs
     '';
 
   inherit lndir;