diff --git a/GNUmakefile b/GNUmakefile
index 651aeac..f404454 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -45,6 +45,7 @@ DEBUG_CFLAGS?=	-g
 ### Mac OS X header selection
 
 ifeq ($(shell uname),Darwin)
+FEATURES+=	-DHAVE_DARWIN_LIBPROC
 XNU_VERSION?=	$(shell uname -a|sed 's/^.*root:xnu-//g'|sed 's/~.*$$//')
 OSX_VERSION?=	$(shell sw_vers -productVersion)
 ifeq ($(wildcard xnu/xnu-$(XNU_VERSION)),)