diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 9bc1f8c3d69a..bbb50a80c3d3 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -151,7 +151,11 @@ __FBSDID("$FreeBSD$");
 #endif
 
 #if !defined(DIAGNOSTIC)
+#ifdef __GNUC_GNU_INLINE__
+#define PMAP_INLINE	inline
+#else
 #define PMAP_INLINE	extern inline
+#endif
 #else
 #define PMAP_INLINE
 #endif
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index bd3376c64a40..72913064e01b 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -162,7 +162,11 @@ __FBSDID("$FreeBSD$");
 #endif
 
 #if !defined(DIAGNOSTIC)
+#ifdef __GNUC_GNU_INLINE__
+#define PMAP_INLINE	inline
+#else
 #define PMAP_INLINE	extern inline
+#endif
 #else
 #define PMAP_INLINE
 #endif
diff --git a/sys/i386/xen/pmap.c b/sys/i386/xen/pmap.c
index 35f006de3e32..cec16636e91e 100644
--- a/sys/i386/xen/pmap.c
+++ b/sys/i386/xen/pmap.c
@@ -173,7 +173,11 @@ __FBSDID("$FreeBSD$");
 #endif
 
 #if !defined(PMAP_DIAGNOSTIC)
+#ifdef __GNUC_GNU_INLINE__
+#define PMAP_INLINE	inline
+#else
 #define PMAP_INLINE	extern inline
+#endif
 #else
 #define PMAP_INLINE
 #endif