diff --git a/pkgs/development/compilers/gcc/4.9/default.nix b/pkgs/development/compilers/gcc/4.9/default.nix
index d328308b063..ed5e9ed920b 100644
--- a/pkgs/development/compilers/gcc/4.9/default.nix
+++ b/pkgs/development/compilers/gcc/4.9/default.nix
@@ -61,10 +61,7 @@ let version = "4.9.3";
     # Whether building a cross-compiler for GNU/Hurd.
     crossGNU = cross != null && cross.config == "i586-pc-gnu";
 
-    # Builds of gfortran have failed with strange errors that we cannot reproduce
-    # (http://hydra.nixos.org/build/23951123). Our best guess is that the build
-    # system has bugs that are exposed by compiling with multiple threads.
-    enableParallelBuilding = !langFortran;
+    enableParallelBuilding = true;
 
     patches = [ ]
       ++ optionals enableParallelBuilding [ ../parallel-bconfig.patch ./parallel-strsignal.patch ]