diff --git a/hw/xfree86/os-support/xf86_OSlib.h b/hw/xfree86/os-support/xf86_OSlib.h
index 5d78c66e3..159c8064c 100644
--- a/hw/xfree86/os-support/xf86_OSlib.h
+++ b/hw/xfree86/os-support/xf86_OSlib.h
@@ -337,13 +337,7 @@ struct pcvtid {
 #define MAXHOSTNAMELEN 32
 #endif                          /* !MAXHOSTNAMELEN */
 
-#if defined(_POSIX_SOURCE)
 #include <limits.h>
-#else
-#define _POSIX_SOURCE
-#include <limits.h>
-#undef _POSIX_SOURCE
-#endif                          /* _POSIX_SOURCE */
 
 #ifndef DEV_MEM
 #define DEV_MEM "/dev/mem"
diff --git a/hw/xfree86/parser/scan.c b/hw/xfree86/parser/scan.c
index 6d46a5621..1eb35ed73 100644
--- a/hw/xfree86/parser/scan.c
+++ b/hw/xfree86/parser/scan.c
@@ -65,14 +65,7 @@
 #include <stdarg.h>
 #include <X11/Xdefs.h>
 #include <X11/Xfuncproto.h>
-
-#if defined(_POSIX_SOURCE)
 #include <limits.h>
-#else
-#define _POSIX_SOURCE
-#include <limits.h>
-#undef _POSIX_SOURCE
-#endif                          /* _POSIX_SOURCE */
 
 #if !defined(MAXHOSTNAMELEN)
 #define MAXHOSTNAMELEN 32
diff --git a/os/osdep.h b/os/osdep.h
index a0d57b8db..c5bec3f56 100644
--- a/os/osdep.h
+++ b/os/osdep.h
@@ -55,14 +55,7 @@ SOFTWARE.
 #include <X11/Xdmcp.h>
 #endif
 
-#ifdef _POSIX_SOURCE
 #include <limits.h>
-#else
-#define _POSIX_SOURCE
-#include <limits.h>
-#undef _POSIX_SOURCE
-#endif
-
 #include <stddef.h>
 #include <X11/Xos.h>
 
diff --git a/os/utils.c b/os/utils.c
index 611e8ac23..1972aa120 100644
--- a/os/utils.c
+++ b/os/utils.c
@@ -83,19 +83,7 @@ __stdcall unsigned long GetTickCount(void);
 #include <X11/fonts/libxfont2.h>
 #include "osdep.h"
 #include "extension.h"
-#ifdef X_POSIX_C_SOURCE
-#define _POSIX_C_SOURCE X_POSIX_C_SOURCE
 #include <signal.h>
-#undef _POSIX_C_SOURCE
-#else
-#if defined(_POSIX_SOURCE)
-#include <signal.h>
-#else
-#define _POSIX_SOURCE
-#include <signal.h>
-#undef _POSIX_SOURCE
-#endif
-#endif
 #ifndef WIN32
 #include <sys/wait.h>
 #endif