diff --git a/nodebuild.h b/nodebuild.h
index 23ed8d7..5eab02c 100644
--- a/nodebuild.h
+++ b/nodebuild.h
@@ -296,7 +296,7 @@ inline int FNodeBuilder::ClassifyLine (node_t &node, const FPrivVert *v1, const
 #ifdef DISABLE_SSE
 	return ClassifyLine2 (node, v1, v2, sidev);
 #else
-#if defined(__SSE2__) || defined(_M_IX64)
+#if defined(__SSE2__) || defined(_M_X64)
 	// If compiling with SSE2 support everywhere, just use the SSE2 version.
 	return ClassifyLineSSE2 (node, v1, v2, sidev);
 #elif defined(_MSC_VER) && _MSC_VER < 1300