diff --git a/pkgs/development/libraries/qt-5/default.nix b/pkgs/development/libraries/qt-5/default.nix
index e593200d1599..e94aecc41e43 100644
--- a/pkgs/development/libraries/qt-5/default.nix
+++ b/pkgs/development/libraries/qt-5/default.nix
@@ -145,7 +145,7 @@ stdenv.mkDerivation rec {
 
   postInstall = if buildDocs then "make docs&&make install_docs" else "";
 
-  enableParallelBuilding = true;
+  #enableParallelBuilding = true; # often fails on Hydra, as well as qt4
 
   meta = {
     homepage = http://qt-project.org;
diff --git a/pkgs/development/tools/misc/gdb/default.nix b/pkgs/development/tools/misc/gdb/default.nix
index d67407eb03df..0d3eb5c824fa 100644
--- a/pkgs/development/tools/misc/gdb/default.nix
+++ b/pkgs/development/tools/misc/gdb/default.nix
@@ -78,7 +78,7 @@ stdenv.mkDerivation rec {
 
     license = "GPLv3+";
 
-    platforms = with platforms; linux ++ cygwin;
+    platforms = with platforms; linux ++ cygwin ++ darwin;
     maintainers = with maintainers; [ pierron ];
   };
 }