diff --git a/config/ac_func_accept_argtypes.m4 b/config/ac_func_accept_argtypes.m4
index 7cb5cb3..1e77179 100644
--- a/config/ac_func_accept_argtypes.m4
+++ b/config/ac_func_accept_argtypes.m4
@@ -38,6 +38,7 @@ dnl
 # 'int' as the result, because that ought to work best.
 #
 # On Win32, accept() returns 'unsigned int PASCAL'
+# Win64 uses SOCKET for return and arg1
 
 AC_DEFUN([AC_FUNC_ACCEPT_ARGTYPES],
 [AC_MSG_CHECKING([types of arguments for accept()])
@@ -45,8 +46,8 @@ AC_DEFUN([AC_FUNC_ACCEPT_ARGTYPES],
  [AC_CACHE_VAL(ac_cv_func_accept_arg1,dnl
   [AC_CACHE_VAL(ac_cv_func_accept_arg2,dnl
    [AC_CACHE_VAL(ac_cv_func_accept_arg3,dnl
-    [for ac_cv_func_accept_return in 'int' 'unsigned int PASCAL'; do
-      for ac_cv_func_accept_arg1 in 'int' 'unsigned int'; do
+    [for ac_cv_func_accept_return in 'int' 'unsigned int PASCAL' 'SOCKET'; do
+      for ac_cv_func_accept_arg1 in 'int' 'unsigned int' 'SOCKET'; do
        for ac_cv_func_accept_arg2 in 'struct sockaddr *' 'const struct sockaddr *' 'void *'; do
         for ac_cv_func_accept_arg3 in 'int' 'size_t' 'socklen_t' 'unsigned int' 'void'; do
          AC_TRY_COMPILE(
diff --git a/configure b/configure
index 8ff61a6..cc809ac 100755
--- a/configure
+++ b/configure
@@ -18696,8 +18696,8 @@ else
      if test "${ac_cv_func_accept_arg3+set}" = set; then
   $as_echo_n "(cached) " >&6
 else
-      for ac_cv_func_accept_return in 'int' 'unsigned int PASCAL'; do
-      for ac_cv_func_accept_arg1 in 'int' 'unsigned int'; do
+      for ac_cv_func_accept_return in 'int' 'unsigned int PASCAL' 'SOCKET'; do
+      for ac_cv_func_accept_arg1 in 'int' 'unsigned int' 'SOCKET'; do
        for ac_cv_func_accept_arg2 in 'struct sockaddr *' 'const struct sockaddr *' 'void *'; do
         for ac_cv_func_accept_arg3 in 'int' 'size_t' 'socklen_t' 'unsigned int' 'void'; do
          cat >conftest.$ac_ext <<_ACEOF
diff --git a/src/include/c.h b/src/include/c.h
index 634b21f..af1be94 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -58,7 +58,7 @@
 #endif
 #include "postgres_ext.h"
 
-#if _MSC_VER >= 1400
+#if _MSC_VER >= 1400 || defined(WIN64)
 #define errcode __msvc_errcode
 #include <crtdefs.h>
 #undef errcode
diff --git a/src/include/port.h b/src/include/port.h
index 7ad464c..4d40cef 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -325,8 +325,12 @@ extern FILE *pgwin32_fopen(const char *, const char *);
 #define		fopen(a,b) pgwin32_fopen(a,b)
 #endif
 
+#ifndef popen
 #define popen(a,b) _popen(a,b)
+#endif
+#ifndef pclose
 #define pclose(a) _pclose(a)
+#endif
 
 /* New versions of MingW have gettimeofday, old mingw and msvc don't */
 #ifndef HAVE_GETTIMEOFDAY
diff --git a/src/include/port/win32.h b/src/include/port/win32.h
index 93439f7..507a61e 100644
--- a/src/include/port/win32.h
+++ b/src/include/port/win32.h
@@ -4,7 +4,9 @@
 #define WIN32_ONLY_COMPILER
 #endif
 
+#ifndef _WIN32_WINNT
 #define _WIN32_WINNT 0x0501
+#endif
 /*
  * Always build with SSPI support. Keep it as a #define in case
  * we want a switch to disable it sometime in the future.
@@ -17,10 +19,12 @@
 #undef mkdir
 
 #undef ERROR
+#ifndef WIN64
 #define _WINSOCKAPI_
-#include <windows.h>
+#endif
 #include <winsock2.h>
 #include <ws2tcpip.h>
+#include <windows.h>
 #undef small
 #include <process.h>
 #include <signal.h>
diff --git a/src/include/port/win32/sys/socket.h b/src/include/port/win32/sys/socket.h
index 6947ec0..edaee6a 100644
--- a/src/include/port/win32/sys/socket.h
+++ b/src/include/port/win32/sys/socket.h
@@ -13,6 +13,7 @@
  */
 #include <winsock2.h>
 #include <ws2tcpip.h>
+#include <windows.h>
 
 #undef ERROR
 #undef small
diff --git a/src/port/getaddrinfo.c b/src/port/getaddrinfo.c
index 654858e..fabd50d 100644
--- a/src/port/getaddrinfo.c
+++ b/src/port/getaddrinfo.c
@@ -329,8 +329,7 @@ gai_strerror(int errcode)
 			return "Not enough memory";
 #endif
 #ifdef EAI_NODATA
-#ifndef WIN32_ONLY_COMPILER		/* MSVC complains because another case has the
-								 * same value */
+#if !defined(WIN64) && !defined(WIN32_ONLY_COMPILER) /* MSVC/WIN64 duplicate */
 		case EAI_NODATA:
 			return "No host data of that type was found";
 #endif
diff --git a/src/test/regress/resultmap b/src/test/regress/resultmap
index 7bfcee2..d02d221 100644
--- a/src/test/regress/resultmap
+++ b/src/test/regress/resultmap
@@ -1,11 +1,14 @@
 float4:out:i.86-pc-mingw32=float4-exp-three-digits.out
+float4:out:x86_64-w64-mingw32=float4-exp-three-digits.out
 float4:out:i.86-pc-win32vc=float4-exp-three-digits.out
 float8:out:i.86-.*-freebsd=float8-small-is-zero.out
 float8:out:i.86-.*-openbsd=float8-small-is-zero.out
 float8:out:i.86-.*-netbsd=float8-small-is-zero.out
 float8:out:m68k-.*-netbsd=float8-small-is-zero.out
 float8:out:i.86-pc-mingw32=float8-exp-three-digits-win32.out
+float8:out:x86_64-w64-mingw32=float8-exp-three-digits-win32.out
 float8:out:i.86-pc-win32vc=float8-exp-three-digits-win32.out
 float8:out:i.86-pc-cygwin=float8-small-is-zero.out
 int8:out:i.86-pc-mingw32=int8-exp-three-digits.out
+int8:out:x86_64-w64-mingw32=int8-exp-three-digits.out
 int8:out:i.86-pc-win32vc=int8-exp-three-digits.out