diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index d3eb691ec5..f7b0cf2efa 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -103,7 +103,7 @@ typedef unsigned LONG_LONG ID;
 
 typedef char ruby_check_sizeof_int[SIZEOF_INT == sizeof(int) ? 1 : -1];
 typedef char ruby_check_sizeof_long[SIZEOF_LONG == sizeof(long) ? 1 : -1];
-#ifdef SIZEOF_LONG_LONG
+#ifdef HAVE_LONG_LONG
 typedef char ruby_check_sizeof_long_long[SIZEOF_LONG_LONG == sizeof(LONG_LONG) ? 1 : -1];
 #endif
 typedef char ruby_check_sizeof_voidp[SIZEOF_VOIDP == sizeof(void*) ? 1 : -1];