diff --git a/gc.c b/gc.c
index 7eaa6975b7..7aa4448d3d 100644
--- a/gc.c
+++ b/gc.c
@@ -2952,17 +2952,6 @@ rb_wb_protected_newobj_of(rb_execution_context_t *ec, VALUE klass, VALUE flags,
     return newobj_of(rb_ec_ractor_ptr(ec), klass, flags, 0, 0, 0, TRUE, size);
 }
 
-VALUE
-rb_newobj_of(VALUE klass, VALUE flags)
-{
-    if ((flags & RUBY_T_MASK) == T_OBJECT) {
-        return rb_class_allocate_instance(klass);
-    }
-    else {
-        return newobj_of(GET_RACTOR(), klass, flags & ~FL_WB_PROTECTED, 0, 0, 0, flags & FL_WB_PROTECTED, RVALUE_SIZE);
-    }
-}
-
 #define UNEXPECTED_NODE(func) \
     rb_bug(#func"(): GC does not handle T_NODE 0x%x(%p) 0x%"PRIxVALUE, \
            BUILTIN_TYPE(obj), (void*)(obj), RBASIC(obj)->flags)
diff --git a/include/ruby/internal/intern/object.h b/include/ruby/internal/intern/object.h
index b9ffa57c06..9daad7d046 100644
--- a/include/ruby/internal/intern/object.h
+++ b/include/ruby/internal/intern/object.h
@@ -151,13 +151,12 @@ VALUE rb_obj_is_kind_of(VALUE obj, VALUE klass);
  * @return     An allocated, not yet initialised instance of `klass`.
  * @note       It calls  the allocator defined by  rb_define_alloc_func().  You
  *             cannot  use   this  function   to  define  an   allocator.   Use
- *             rb_newobj_of(), #TypedData_Make_Struct or others, instead.
+ *             TypedData_Make_Struct or others, instead.
  * @note       Usually  prefer  rb_class_new_instance() to  rb_obj_alloc()  and
  *             rb_obj_call_init().
  * @see        rb_class_new_instance()
  * @see        rb_obj_call_init()
  * @see        rb_define_alloc_func()
- * @see        rb_newobj_of()
  * @see        #TypedData_Make_Struct
  */
 VALUE rb_obj_alloc(VALUE klass);
diff --git a/include/ruby/internal/intern/vm.h b/include/ruby/internal/intern/vm.h
index 76af796b54..29e0c7f534 100644
--- a/include/ruby/internal/intern/vm.h
+++ b/include/ruby/internal/intern/vm.h
@@ -229,8 +229,7 @@ void rb_define_alloc_func(VALUE klass, rb_alloc_func_t func);
  * restrict creation  of an instance of  a class.  For example  it rarely makes
  * sense for  a DB adaptor class  to allow programmers creating  DB row objects
  * without querying  the DB  itself.  You  can kill  sporadic creation  of such
- * objects then,  by nullifying  the allocator function  using this  API.  Your
- * object shall be allocated using #RB_NEWOBJ_OF() directly.
+ * objects then,  by nullifying  the allocator function  using this  API.
  *
  * @param[out]  klass  The class to modify.
  * @pre         `klass` must be an instance of Class.
diff --git a/include/ruby/internal/newobj.h b/include/ruby/internal/newobj.h
index a990682d0c..6eee2fa5fa 100644
--- a/include/ruby/internal/newobj.h
+++ b/include/ruby/internal/newobj.h
@@ -29,40 +29,14 @@
 #include "ruby/internal/value.h"
 #include "ruby/assert.h"
 
-/**
- * Identical  to #RB_NEWOBJ,  except it  also accepts  the allocating  object's
- * class and flags.
- *
- * @param      obj             Variable name.
- * @param      type            Variable type.
- * @param      klass           Object's class.
- * @param      flags           Object's flags.
- * @exception  rb_eNoMemError  No space left.
- * @return     An allocated object, filled with the arguments.
- */
-#define RB_NEWOBJ_OF(obj,type,klass,flags) type *(obj) = RBIMPL_CAST((type *)rb_newobj_of(klass, flags))
-
-#define NEWOBJ_OF  RB_NEWOBJ_OF   /**< @old{RB_NEWOBJ_OF} */
 #define OBJSETUP   rb_obj_setup   /**< @old{rb_obj_setup} */
 #define CLONESETUP rb_clone_setup /**< @old{rb_clone_setup} */
 #define DUPSETUP   rb_dup_setup   /**< @old{rb_dup_setup} */
 
 RBIMPL_SYMBOL_EXPORT_BEGIN()
-
-/**
- * This is the implementation detail of #RB_NEWOBJ_OF.
- *
- * @param      klass           Object's class.
- * @param      flags           Object's flags.
- * @exception  rb_eNoMemError  No space left.
- * @return     An allocated object, filled with the arguments.
- */
-VALUE rb_newobj_of(VALUE klass, VALUE flags);
-
 /**
  * Fills common fields in the object.
  *
- * @note           Prefer rb_newobj_of() to this function.
  * @param[in,out]  obj    A Ruby object to be set up.
  * @param[in]      klass  `obj` will belong to this class.
  * @param[in]      type   One of ::ruby_value_type.
diff --git a/internal.h b/internal.h
index c66e057f60..4fb99d1c08 100644
--- a/internal.h
+++ b/internal.h
@@ -40,10 +40,6 @@
 #undef RClass
 #undef RCLASS_SUPER
 
-/* internal/gc.h */
-#undef NEWOBJ_OF
-#undef RB_NEWOBJ_OF
-
 /* internal/hash.h */
 #undef RHASH_IFNONE
 #undef RHASH_SIZE
diff --git a/internal/gc.h b/internal/gc.h
index 9435f26ffd..e9081ffaa6 100644
--- a/internal/gc.h
+++ b/internal/gc.h
@@ -121,11 +121,6 @@ size_t rb_size_pool_slot_size(unsigned char pool_id);
 struct rb_execution_context_struct; /* in vm_core.h */
 struct rb_objspace; /* in vm_core.h */
 
-#ifdef NEWOBJ_OF
-# undef NEWOBJ_OF
-# undef RB_NEWOBJ_OF
-#endif
-
 #define NEWOBJ_OF(var, T, c, f, s, ec) \
     T *(var) = (T *)(((f) & FL_WB_PROTECTED) ? \
             rb_wb_protected_newobj_of((ec ? ec : GET_EC()), (c), (f) & ~FL_WB_PROTECTED, s) : \
diff --git a/spec/ruby/optional/capi/ext/object_spec.c b/spec/ruby/optional/capi/ext/object_spec.c
index 7023c29bdb..1d3a1ed476 100644
--- a/spec/ruby/optional/capi/ext/object_spec.c
+++ b/spec/ruby/optional/capi/ext/object_spec.c
@@ -388,16 +388,8 @@ static VALUE object_spec_rb_ivar_foreach(VALUE self, VALUE obj) {
 }
 
 static VALUE speced_allocator(VALUE klass) {
-  VALUE flags = 0;
-  VALUE instance;
-  if (RTEST(rb_class_inherited_p(klass, rb_cString))) {
-    flags = T_STRING;
-  } else if (RTEST(rb_class_inherited_p(klass, rb_cArray))) {
-    flags = T_ARRAY;
-  } else {
-    flags = T_OBJECT;
-  }
-  instance = rb_newobj_of(klass, flags);
+  VALUE super = rb_class_get_superclass(klass);
+  VALUE instance = rb_get_alloc_func(super)(klass);
   rb_iv_set(instance, "@from_custom_allocator", Qtrue);
   return instance;
 }