diff --git a/pkgs/development/libraries/boehm-gc/default.nix b/pkgs/development/libraries/boehm-gc/default.nix
index 0983edbcdd2..025ad6c1dc8 100644
--- a/pkgs/development/libraries/boehm-gc/default.nix
+++ b/pkgs/development/libraries/boehm-gc/default.nix
@@ -44,3 +44,10 @@ stdenv.mkDerivation {
     platforms = stdenv.lib.platforms.all;
   };
 }
+
+//
+
+(if stdenv.system == "x86_64-darwin"
+ # Fix "#error ucontext routines are deprecated, and require _XOPEN_SOURCE to be defined".
+ then { configureFlags = "CPPFLAGS=-D_XOPEN_SOURCE"; }
+ else {})