ensure T_OBJECT objects have internals initialized

gc.c

@@ -2304,7 +2304,11 @@ rb_newobj(void)
 VALUE
 rb_newobj_of(VALUE klass, VALUE flags)
 {
-    return newobj_of(klass, flags & ~FL_WB_PROTECTED, 0, 0, 0, flags & FL_WB_PROTECTED);
+    if ((flags & RUBY_T_MASK) == T_OBJECT) {
+        return newobj_of(klass, (flags | ROBJECT_EMBED) & ~FL_WB_PROTECTED , Qundef, Qundef, Qundef, flags & FL_WB_PROTECTED);
+    } else {
+        return newobj_of(klass, flags & ~FL_WB_PROTECTED, 0, 0, 0, flags & FL_WB_PROTECTED);
+    }
 }
 
 #define UNEXPECTED_NODE(func) \