diff --git a/yjit.h b/yjit.h
index c500fb1a69..cc1e23d327 100644
--- a/yjit.h
+++ b/yjit.h
@@ -16,7 +16,7 @@
 #endif
 
 // We generate x86 assembly
-#if defined(__x86_64__)
+#if (defined(__x86_64__) && !defined(_WIN32)) || (defined(_WIN32) && defined(_M_AMD64)) // x64 platforms without mingw/msys
 # define YJIT_SUPPORTED_P 1
 #else
 # define YJIT_SUPPORTED_P 0