diff --git a/lib/zig.h b/lib/zig.h
index ea63467708..c5e9516f46 100644
--- a/lib/zig.h
+++ b/lib/zig.h
@@ -237,6 +237,8 @@ typedef char bool;
 
 #if zig_has_builtin(unreachable) || defined(zig_gnuc) || defined(zig_tinyc)
 #define zig_unreachable() __builtin_unreachable()
+#elif defined(zig_msvc)
+#define zig_unreachable() __assume(0)
 #else
 #define zig_unreachable()
 #endif