diff --git a/include/string.h b/include/string.h
index dc0580798f52..7b3dbc68b69c 100644
--- a/include/string.h
+++ b/include/string.h
@@ -81,13 +81,16 @@ char	*strstr(const char *, const char *);
 char	*strtok(char * __restrict, const char * __restrict);
 size_t	 strxfrm(char * __restrict, const char * __restrict, size_t);
 
-#if __POSIX_VISIBLE >= 200112
+#if __POSIX_VISIBLE >= 200112 || __XSI_VISIBLE >= 500
 void	*memccpy(void * __restrict, const void * __restrict, int, size_t);
 char	*strdup(const char *);
-int	 strerror_r(int, char *, size_t);
 char	*strtok_r(char *, const char *, char **);
 #endif
 
+#if __POSIX_VISIBLE >= 200112
+int	 strerror_r(int, char *, size_t);
+#endif
+
 #if __BSD_VISIBLE
 char	*strcasestr(const char *, const char *);
 size_t	 strlcat(char *, const char *, size_t);