diff --git a/vm/Config.macosx b/vm/Config.macosx
index d989a439be..07629f72bb 100644
--- a/vm/Config.macosx
+++ b/vm/Config.macosx
@@ -1,5 +1,5 @@
 include vm/Config.unix
-CFLAGS += -fPIC -D_XOPEN_SOURCE
+CFLAGS += -fPIC
 
 PLAF_DLL_OBJS += vm/os-macosx.o vm/mach_signal.o
 
diff --git a/vm/os-macosx-ppc.hpp b/vm/os-macosx-ppc.hpp
index d80959eaec..84fe50c283 100644
--- a/vm/os-macosx-ppc.hpp
+++ b/vm/os-macosx-ppc.hpp
@@ -1,4 +1,4 @@
-#include <ucontext.h>
+#include <sys/ucontext.h>
 
 namespace factor
 {
diff --git a/vm/os-macosx-x86.32.hpp b/vm/os-macosx-x86.32.hpp
index e6454fd039..036dc1a398 100644
--- a/vm/os-macosx-x86.32.hpp
+++ b/vm/os-macosx-x86.32.hpp
@@ -1,4 +1,4 @@
-#include <ucontext.h>
+#include <sys/ucontext.h>
 
 namespace factor
 {
diff --git a/vm/os-macosx-x86.64.hpp b/vm/os-macosx-x86.64.hpp
index 4d8976991e..f9d54d875f 100644
--- a/vm/os-macosx-x86.64.hpp
+++ b/vm/os-macosx-x86.64.hpp
@@ -1,4 +1,4 @@
-#include <ucontext.h>
+#include <sys/ucontext.h>
 
 namespace factor
 {