diff --git a/struct.c b/struct.c
index f0307916b3..17e53ab4e0 100644
--- a/struct.c
+++ b/struct.c
@@ -429,6 +429,9 @@ rb_struct_new(VALUE klass, ...)
     return rb_class_new_instance(size, mem, klass);
 }
 
+static VALUE
+rb_struct_size(VALUE s);
+
 /*
  *  call-seq:
  *     struct.each {|obj| block }  -> struct
@@ -455,7 +458,7 @@ rb_struct_each(VALUE s)
 {
     long i;
 
-    RETURN_ENUMERATOR(s, 0, 0);
+    RETURN_SIZED_ENUMERATOR(s, 0, 0, rb_struct_size);
     for (i=0; i<RSTRUCT_LEN(s); i++) {
 	rb_yield(RSTRUCT_PTR(s)[i]);
     }
@@ -489,7 +492,7 @@ rb_struct_each_pair(VALUE s)
     VALUE members;
     long i;
 
-    RETURN_ENUMERATOR(s, 0, 0);
+    RETURN_SIZED_ENUMERATOR(s, 0, 0, rb_struct_size);
     members = rb_struct_members(s);
     for (i=0; i<RSTRUCT_LEN(s); i++) {
 	rb_yield_values(2, rb_ary_entry(members, i), RSTRUCT_PTR(s)[i]);
@@ -793,7 +796,7 @@ rb_struct_select(int argc, VALUE *argv, VALUE s)
     long i;
 
     rb_check_arity(argc, 0, 0);
-    RETURN_ENUMERATOR(s, 0, 0);
+    RETURN_SIZED_ENUMERATOR(s, 0, 0, rb_struct_size);
     result = rb_ary_new();
     for (i = 0; i < RSTRUCT_LEN(s); i++) {
 	if (RTEST(rb_yield(RSTRUCT_PTR(s)[i]))) {
diff --git a/test/ruby/test_enumerator.rb b/test/ruby/test_enumerator.rb
index 884f8c6b27..c45e3eb0a7 100644
--- a/test/ruby/test_enumerator.rb
+++ b/test/ruby/test_enumerator.rb
@@ -456,6 +456,13 @@ class TestEnumerator < Test::Unit::TestCase
     end
   end
 
+  def test_size_for_enum_created_from_struct
+    s = Struct.new(:foo, :bar, :baz).new(1, 2)
+    %i[each each_pair select].each do |method|
+      assert_equal 3, s.send(method).size
+    end
+  end
+
   def check_consistency_for_combinatorics(method)
     [ [], [:a, :b, :c, :d, :e] ].product([-2, 0, 2, 5, 6]) do |array, arg|
       assert_equal array.send(method, arg).to_a.size, array.send(method, arg).size,