diff --git a/libavutil/x86/x86inc.asm b/libavutil/x86/x86inc.asm
index cb3f82b21a..d07e171497 100644
--- a/libavutil/x86/x86inc.asm
+++ b/libavutil/x86/x86inc.asm
@@ -49,6 +49,8 @@
         %define WIN64  1
     %elifidn __OUTPUT_FORMAT__,win64
         %define WIN64  1
+    %elifidn __OUTPUT_FORMAT__,x64
+        %define WIN64  1
     %else
         %define UNIX64 1
     %endif