diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 6a198f94e4..1c74b121e8 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -4358,6 +4358,7 @@ static VALUE
 vm_opt_regexpmatch2(VALUE recv, VALUE obj)
 {
     if (CLASS_OF(recv) == rb_cString &&
+        CLASS_OF(obj) == rb_cRegexp &&
 	BASIC_OP_UNREDEFINED_P(BOP_MATCH, STRING_REDEFINED_OP_FLAG)) {
 	return rb_reg_match(obj, recv);
     }