diff --git a/vm_core.h b/vm_core.h
index 176ec9d333..5c6f6fb689 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -63,7 +63,7 @@
  *   2: succinct bitvector
  */
 #ifndef VM_INSN_INFO_TABLE_IMPL
-# define VM_INSN_INFO_TABLE_IMPL 2
+# define VM_INSN_INFO_TABLE_IMPL 1
 #endif
 
 #include "ruby/ruby.h"