diff --git a/lib/hostip.h b/lib/hostip.h
index e987f301e..85425b6ce 100644
--- a/lib/hostip.h
+++ b/lib/hostip.h
@@ -37,38 +37,13 @@
 #endif
 
 /*
- * Setup comfortable CURLRES_* defines to use in the host*.c sources.
+ * Comfortable CURLRES_* definitions are included from setup.h
  */
 
 #ifdef USE_ARES
 #include <ares_version.h>
 #endif
 
-#ifdef USE_ARES
-#define CURLRES_ASYNCH
-#define CURLRES_ARES
-#endif
-
-#ifdef USE_THREADING_GETHOSTBYNAME
-#define CURLRES_ASYNCH
-#define CURLRES_THREADED
-#endif
-
-#ifdef USE_THREADING_GETADDRINFO
-#define CURLRES_ASYNCH
-#define CURLRES_THREADED
-#endif
-
-#ifdef ENABLE_IPV6
-#define CURLRES_IPV6
-#else
-#define CURLRES_IPV4
-#endif
-
-#ifndef CURLRES_ASYNCH
-#define CURLRES_SYNCH
-#endif
-
 /* Allocate enough memory to hold the full name information structs and
  * everything. OSF1 is known to require at least 8872 bytes. The buffer
  * required for storing all possible aliases and IP numbers is according to
diff --git a/lib/setup.h b/lib/setup.h
index a8549a7d8..980a91699 100644
--- a/lib/setup.h
+++ b/lib/setup.h
@@ -407,6 +407,27 @@
 
 #endif /* WIN32 */
 
+/*
+ * msvc 6.0 requires PSDK in order to have INET6_ADDRSTRLEN
+ * defined in ws2tcpip.h as well as to provide IPv6 support.
+ */
+
+#if defined(_MSC_VER) && !defined(__POCC__)
+#  if !defined(HAVE_WS2TCPIP_H) || \
+     ((_MSC_VER < 1300) && !defined(INET6_ADDRSTRLEN))
+#    undef HAVE_GETADDRINFO_THREADSAFE
+#    undef HAVE_FREEADDRINFO
+#    undef HAVE_GETADDRINFO
+#    undef HAVE_GETNAMEINFO
+#    undef ENABLE_IPV6
+#  endif
+#endif
+
+/* ---------------------------------------------------------------- */
+/*             resolver specialty compile-time defines              */
+/*         CURLRES_* defines to use in the host*.c sources          */
+/* ---------------------------------------------------------------- */
+
 #if defined(WIN32) && !defined(__CYGWIN__) && !defined(USE_ARES) && \
     !defined(__LCC__)  /* lcc-win32 doesn't have _beginthreadex() */
 #ifdef ENABLE_IPV6
@@ -424,6 +445,33 @@
 #define CURL_NO__BEGINTHREADEX
 #endif
 
+#ifdef USE_ARES
+#  define CURLRES_ASYNCH
+#  define CURLRES_ARES
+#endif
+
+#ifdef USE_THREADING_GETHOSTBYNAME
+#  define CURLRES_ASYNCH
+#  define CURLRES_THREADED
+#endif
+
+#ifdef USE_THREADING_GETADDRINFO
+#  define CURLRES_ASYNCH
+#  define CURLRES_THREADED
+#endif
+
+#ifdef ENABLE_IPV6
+#  define CURLRES_IPV6
+#else
+#  define CURLRES_IPV4
+#endif
+
+#ifndef CURLRES_ASYNCH
+#  define CURLRES_SYNCH
+#endif
+
+/* ---------------------------------------------------------------- */
+
 /*
  * When using WINSOCK, TELNET protocol requires WINSOCK2 API.
  */
@@ -444,20 +492,6 @@
 #  endif
 #endif
 
-/*
- * msvc 6.0 requires PSDK in order to have INET6_ADDRSTRLEN
- * defined in ws2tcpip.h as well as to provide IPv6 support.
- */
-
-#if defined(_MSC_VER) && !defined(__POCC__)
-#  if !defined(HAVE_WS2TCPIP_H) || ((_MSC_VER < 1300) && !defined(INET6_ADDRSTRLEN))
-#    undef HAVE_FREEADDRINFO
-#    undef HAVE_GETADDRINFO
-#    undef HAVE_GETNAMEINFO
-#    undef ENABLE_IPV6
-#  endif
-#endif
-
 /*
  * Intentionally fail to build when using msvc 6.0 without PSDK installed.
  * The brave of heart can circumvent this, defining ALLOW_MSVC6_WITHOUT_PSDK
diff --git a/lib/url.c b/lib/url.c
index f3ac14d5c..927e16887 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -5044,8 +5044,7 @@ CURLcode Curl_connect(struct SessionHandle *data,
 CURLcode Curl_async_resolved(struct connectdata *conn,
                              bool *protocol_done)
 {
-#if defined(USE_ARES) || defined(USE_THREADING_GETHOSTBYNAME) || \
-    defined(USE_THREADING_GETADDRINFO)
+#ifdef CURLRES_ASYNCH
   CURLcode code;
 
   if(conn->async.dns) {
diff --git a/lib/urldata.h b/lib/urldata.h
index 8e3f612ce..f02bfc43d 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -436,8 +436,7 @@ typedef enum {
 } zlibInitState;
 #endif
 
-#if defined(USE_ARES) || defined(USE_THREADING_GETHOSTBYNAME) || \
-    defined(USE_THREADING_GETADDRINFO)
+#ifdef CURLRES_ASYNCH
 struct Curl_async {
   char *hostname;
   int port;
@@ -813,8 +812,7 @@ struct connectdata {
 
   char syserr_buf [256]; /* buffer for Curl_strerror() */
 
-#if defined(USE_ARES) || defined(USE_THREADING_GETHOSTBYNAME) || \
-    defined(USE_THREADING_GETADDRINFO)
+#ifdef CURLRES_ASYNCH
   /* data used for the asynch name resolve callback */
   struct Curl_async async;
 #endif