diff --git a/ares/setup.h b/ares/setup.h
index 70af3be3c..3b97e273e 100644
--- a/ares/setup.h
+++ b/ares/setup.h
@@ -69,6 +69,22 @@
 #  endif
 #endif
 
+/*
+ * Define USE_WINSOCK to 2 if we have and use WINSOCK2 API, else
+ * define USE_WINSOCK to 1 if we have and use WINSOCK  API, else
+ * undefine USE_WINSOCK.
+ */
+
+#undef USE_WINSOCK
+
+#ifdef HAVE_WINSOCK2_H
+#  define USE_WINSOCK 2
+#else
+#  ifdef HAVE_WINSOCK_H
+#    define USE_WINSOCK 1
+#  endif
+#endif
+
 /*
  * Work-arounds for systems without configure support
  */
diff --git a/lib/setup.h b/lib/setup.h
index a02834ecd..6bcde3d5c 100644
--- a/lib/setup.h
+++ b/lib/setup.h
@@ -103,6 +103,22 @@
 #  endif
 #endif
 
+/*
+ * Define USE_WINSOCK to 2 if we have and use WINSOCK2 API, else
+ * define USE_WINSOCK to 1 if we have and use WINSOCK  API, else
+ * undefine USE_WINSOCK.
+ */
+
+#undef USE_WINSOCK
+
+#ifdef HAVE_WINSOCK2_H
+#  define USE_WINSOCK 2
+#else
+#  ifdef HAVE_WINSOCK_H
+#    define USE_WINSOCK 1
+#  endif
+#endif
+
 
 #ifndef TRUE
 #define TRUE 1
diff --git a/src/setup.h b/src/setup.h
index 6e0f23a15..139b7467f 100644
--- a/src/setup.h
+++ b/src/setup.h
@@ -105,6 +105,23 @@
 #  endif
 #endif
 
+/*
+ * Define USE_WINSOCK to 2 if we have and use WINSOCK2 API, else
+ * define USE_WINSOCK to 1 if we have and use WINSOCK  API, else
+ * undefine USE_WINSOCK.
+ */
+
+#undef USE_WINSOCK
+
+#ifdef HAVE_WINSOCK2_H
+#  define USE_WINSOCK 2
+#else
+#  ifdef HAVE_WINSOCK_H
+#    define USE_WINSOCK 1
+#  endif
+#endif
+
+
 #include <stdio.h>
 
 #ifdef __TANDEM