diff --git a/configure.ac b/configure.ac
index b9a5b24..5d43d53 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1431,8 +1431,7 @@
 
 case $host_cpu in
   *i[[3456789]]86*) WINE_CHECK_DEFINE([__i386__]) ;;
-  *x86_64*)         WINE_CHECK_DEFINE([__x86_64__])
-                    WINE_CHECK_DEFINE([_WIN64]) ;;
+  *x86_64*)         WINE_CHECK_DEFINE([__x86_64__]) ;;
   *alpha*)          WINE_CHECK_DEFINE([__ALPHA__]) ;;
   *sparc*)          WINE_CHECK_DEFINE([__sparc__]) ;;
   *powerpc*)        WINE_CHECK_DEFINE([__powerpc__]) ;;