diff --git histlib.h histlib.h
index c938a10..925ab72 100644
--- histlib.h
+++ histlib.h
@@ -51,9 +51,9 @@
 #endif
 
 #ifndef member
-#  ifndef strchr
+#  if !defined (strchr) && !defined (__STDC__)
 extern char *strchr ();
-#  endif
+#  endif /* !strchr && !__STDC__ */
 #define member(c, s) ((c) ? ((char *)strchr ((s), (c)) != (char *)NULL) : 0)
 #endif