diff --git a/binding.gyp b/binding.gyp
index f2cbbf9..ad5d91c 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -5,7 +5,7 @@
 			[
 				"OS == 'mac'",
 				{
-					"pkg_env": "PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig"
+					"pkg_env": "PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/opt/X11/lib/pkgconfig:/usr/local/opt/libffi/lib/pkgconfig"
 				},
 				{
 					"pkg_env": ""