diff --git a/src/third_party/IntelRDFPMathLib20U1/LIBRARY/float128/architecture.h b/src/third_party/IntelRDFPMathLib20U1/LIBRARY/float128/architecture.h
index ef8a5b7..98d86c1 100644
--- a/src/third_party/IntelRDFPMathLib20U1/LIBRARY/float128/architecture.h
+++ b/src/third_party/IntelRDFPMathLib20U1/LIBRARY/float128/architecture.h
@@ -39,7 +39,7 @@
 #   define merced
 #endif
 
-#if defined(ct) || defined(efi2)
+#if defined(ct) || defined(efi2) || defined(__x86_64__)
 #   undef  _M_AMD64
 #   define _M_AMD64
 #endif