diff --git a/sys/amd64/include/limits.h b/sys/amd64/include/limits.h
--- a/sys/amd64/include/limits.h
+++ b/sys/amd64/include/limits.h
@@ -35,11 +35,7 @@
 #ifndef _MACHINE_LIMITS_H_
 #define	_MACHINE_LIMITS_H_
 
-#include <sys/cdefs.h>
-
-#ifdef __CC_SUPPORTS_WARNING
 #warning "machine/limits.h is deprecated.  Include sys/limits.h instead."
-#endif
 
 #include <sys/limits.h>
 
diff --git a/sys/arm/include/limits.h b/sys/arm/include/limits.h
--- a/sys/arm/include/limits.h
+++ b/sys/arm/include/limits.h
@@ -35,11 +35,7 @@
 #ifndef _MACHINE_LIMITS_H_
 #define	_MACHINE_LIMITS_H_
 
-#include <sys/cdefs.h>
-
-#ifdef __CC_SUPPORTS_WARNING
 #warning "machine/limits.h is deprecated.  Include sys/limits.h instead."
-#endif
 
 #include <sys/limits.h>
 
diff --git a/sys/i386/include/limits.h b/sys/i386/include/limits.h
--- a/sys/i386/include/limits.h
+++ b/sys/i386/include/limits.h
@@ -35,11 +35,7 @@
 #ifndef _MACHINE_LIMITS_H_
 #define	_MACHINE_LIMITS_H_
 
-#include <sys/cdefs.h>
-
-#ifdef __CC_SUPPORTS_WARNING
 #warning "machine/limits.h is deprecated.  Include sys/limits.h instead."
-#endif
 
 #include <sys/limits.h>
 
diff --git a/sys/i386/include/speaker.h b/sys/i386/include/speaker.h
--- a/sys/i386/include/speaker.h
+++ b/sys/i386/include/speaker.h
@@ -5,11 +5,7 @@
 #ifndef	_MACHINE_SPEAKER_H_
 #define	_MACHINE_SPEAKER_H_
 
-#include <sys/cdefs.h>
-
-#ifdef __CC_SUPPORTS_WARNING
 #warning "machine/speaker.h is deprecated.  Include dev/speaker/speaker.h instead."
-#endif
 
 #include <dev/speaker/speaker.h>
 
diff --git a/sys/powerpc/include/limits.h b/sys/powerpc/include/limits.h
--- a/sys/powerpc/include/limits.h
+++ b/sys/powerpc/include/limits.h
@@ -35,11 +35,7 @@
 #ifndef _MACHINE_LIMITS_H_
 #define	_MACHINE_LIMITS_H_
 
-#include <sys/cdefs.h>
-
-#ifdef __CC_SUPPORTS_WARNING
 #warning "machine/limits.h is deprecated.  Include sys/limits.h instead."
-#endif
 
 #include <sys/limits.h>
 
diff --git a/sys/sys/syslimits.h b/sys/sys/syslimits.h
--- a/sys/sys/syslimits.h
+++ b/sys/sys/syslimits.h
@@ -36,13 +36,8 @@
 #define _SYS_SYSLIMITS_H_
 
 #if !defined(_STANDALONE) && !defined(_KERNEL) && !defined(_LIMITS_H_) && !defined(_SYS_PARAM_H_)
-#ifndef _SYS_CDEFS_H_
-#error this file needs sys/cdefs.h as a prerequisite
-#endif
-#ifdef __CC_SUPPORTS_WARNING
 #warning "No user-serviceable parts inside."
 #endif
-#endif
 
 /*
  * Do not add any new variables here.  (See the comment at the end of