diff --git a/pkgs/development/libraries/qt-4.x/4.8/default.nix b/pkgs/development/libraries/qt-4.x/4.8/default.nix
index 0d6716243b8..1679b4953e7 100644
--- a/pkgs/development/libraries/qt-4.x/4.8/default.nix
+++ b/pkgs/development/libraries/qt-4.x/4.8/default.nix
@@ -121,7 +121,9 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ perl pkgconfig which ];
 
-  enableParallelBuilding = true;
+  # occasional build problems if one has too many cores (like on Hydra)
+  # @vcunat has been unable to find a *reliable* fix
+  enableParallelBuilding = false;
 
   NIX_CFLAGS_COMPILE = optionalString stdenv.isDarwin
     "-I${glib}/include/glib-2.0 -I${glib}/lib/glib-2.0/include";