diff --git a/include/strings.h b/include/strings.h
index f6a002447cdc..078ce1b5f5fb 100644
--- a/include/strings.h
+++ b/include/strings.h
@@ -38,10 +38,14 @@ typedef	__size_t	size_t;
 #endif
 
 __BEGIN_DECLS
+#if __BSD_VISIBLE || __POSIX_VISIBLE <= 200112
 int	 bcmp(const void *, const void *, size_t) __pure;	/* LEGACY */
 void	 bcopy(const void *, void *, size_t);			/* LEGACY */
 void	 bzero(void *, size_t);					/* LEGACY */
+#endif
+#if __XSI_VISIBLE
 int	 ffs(int) __pure2;
+#endif
 #ifdef __BSD_VISIBLE
 int	 ffsl(long) __pure2;
 int	 ffsll(long long) __pure2;
@@ -49,8 +53,10 @@ int	 fls(int) __pure2;
 int	 flsl(long) __pure2;
 int	 flsll(long long) __pure2;
 #endif
+#if __BSD_VISIBLE || __POSIX_VISIBLE <= 200112
 char	*index(const char *, int) __pure;			/* LEGACY */
 char	*rindex(const char *, int) __pure;			/* LEGACY */
+#endif
 int	 strcasecmp(const char *, const char *) __pure;
 int	 strncasecmp(const char *, const char *, size_t) __pure;
 __END_DECLS