diff --git a/include/msvcrt/crtdefs.h b/include/msvcrt/crtdefs.h
index 06ce9c34ca5..da278be003f 100644
--- a/include/msvcrt/crtdefs.h
+++ b/include/msvcrt/crtdefs.h
@@ -29,7 +29,7 @@
 # error You cannot use both wine/port.h and msvcrt headers
 #endif
 
-#if (defined(__x86_64__) || defined(__powerpc64__) || defined(__sparc64__)) && !defined(_WIN64)
+#if (defined(__x86_64__) || defined(__powerpc64__) || defined(__sparc64__) || defined(__aarch64__)) && !defined(_WIN64)
 #define _WIN64
 #endif
 
diff --git a/include/windef.h b/include/windef.h
index eb5935322b5..17c0fba5d5e 100644
--- a/include/windef.h
+++ b/include/windef.h
@@ -37,7 +37,7 @@ extern "C" {
 
 /* Calling conventions definitions */
 
-#if (defined(__x86_64__) || defined(__powerpc64__) || defined(__sparc64__)) && !defined(_WIN64)
+#if (defined(__x86_64__) || defined(__powerpc64__) || defined(__sparc64__) || defined(__aarch64__)) && !defined(_WIN64)
 #define _WIN64
 #endif