diff --git a/src/x86/ffi.c b/src/x86/ffi.c
index a02a8a19..e1f24471 100644
--- a/src/x86/ffi.c
+++ b/src/x86/ffi.c
@@ -318,7 +318,9 @@ ffi_status ffi_prep_cif_machdep(ffi_cif *cif)
 #endif
 
 #ifndef X86_WIN32
+#ifndef X86_WIN64
   if (cif->abi != FFI_STDCALL && cif->abi != FFI_THISCALL && cif->abi != FFI_FASTCALL)
+#endif
     cif->bytes = (cif->bytes + 15) & ~0xF;
 #endif