diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index e152d3ffea91..9e472e7aaac2 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -153,7 +153,7 @@ __FBSDID("$FreeBSD$");
 #endif
 
 #if !defined(DIAGNOSTIC)
-#define PMAP_INLINE	__gnu89_inline
+#define PMAP_INLINE	extern inline
 #else
 #define PMAP_INLINE
 #endif
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index 5d7dc979a9cd..307587a88c4e 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -161,7 +161,7 @@ __FBSDID("$FreeBSD$");
 #endif
 
 #if !defined(DIAGNOSTIC)
-#define PMAP_INLINE	__gnu89_inline
+#define PMAP_INLINE	extern inline
 #else
 #define PMAP_INLINE
 #endif
diff --git a/sys/i386/xen/pmap.c b/sys/i386/xen/pmap.c
index 59947e8245f7..28835963a3de 100644
--- a/sys/i386/xen/pmap.c
+++ b/sys/i386/xen/pmap.c
@@ -172,7 +172,7 @@ __FBSDID("$FreeBSD$");
 #endif
 
 #if !defined(PMAP_DIAGNOSTIC)
-#define PMAP_INLINE	__gnu89_inline
+#define PMAP_INLINE	extern inline
 #else
 #define PMAP_INLINE
 #endif
diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index 44bed25ecca1..5d413d3710f1 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -234,12 +234,6 @@
 #define	__always_inline
 #endif
 
-#if __GNUC_PREREQ__(4, 2) /* actually 4.1.3 */
-#define	__gnu89_inline	__attribute__((__gnu_inline__)) __inline
-#else
-#define	__gnu89_inline
-#endif
-
 #if __GNUC_PREREQ__(3, 1)
 #define	__noinline	__attribute__ ((__noinline__))
 #else