diff --git a/lib/ostruct.rb b/lib/ostruct.rb
index 9b44d4a88a..f403f63bdb 100644
--- a/lib/ostruct.rb
+++ b/lib/ostruct.rb
@@ -212,7 +212,7 @@ class OpenStruct
     super
   end
 
-  def method_missing(mid, *args) # :nodoc:
+  private def method_missing(mid, *args) # :nodoc:
     len = args.length
     if mname = mid[/.*(?==\z)/m]
       if len != 1
diff --git a/spec/ruby/library/openstruct/method_missing_spec.rb b/spec/ruby/library/openstruct/method_missing_spec.rb
index 1992b7255c..212db015a9 100644
--- a/spec/ruby/library/openstruct/method_missing_spec.rb
+++ b/spec/ruby/library/openstruct/method_missing_spec.rb
@@ -7,43 +7,20 @@ describe "OpenStruct#method_missing when called with a method name ending in '='
   end
 
   it "raises an ArgumentError when not passed any additional arguments" do
-    -> { @os.method_missing(:test=) }.should raise_error(ArgumentError)
-  end
-
-  it "raises a TypeError when self is frozen" do
-    @os.freeze
-    -> { @os.method_missing(:test=, "test") }.should raise_error(RuntimeError)
-  end
-
-  it "creates accessor methods" do
-    @os.method_missing(:test=, "test")
-    @os.respond_to?(:test=).should be_true
-    @os.respond_to?(:test).should be_true
-
-    @os.test.should == "test"
-    @os.test = "changed"
-    @os.test.should == "changed"
+    -> { @os.send(:test=) }.should raise_error(ArgumentError)
   end
 end
 
 describe "OpenStruct#method_missing when passed additional arguments" do
   it "raises a NoMethodError when the key does not exist" do
     os = OpenStruct.new
-    -> { os.method_missing(:test, 1, 2, 3) }.should raise_error(NoMethodError)
+    -> { os.test(1, 2, 3) }.should raise_error(NoMethodError)
   end
 
   ruby_version_is "2.7" do
     it "raises an ArgumentError when the key exists" do
       os = OpenStruct.new(test: 20)
-      -> { os.method_missing(:test, 1, 2, 3) }.should raise_error(ArgumentError)
+      -> { os.test(1, 2, 3) }.should raise_error(ArgumentError)
     end
   end
 end
-
-describe "OpenStruct#method_missing when not passed any additional arguments" do
-  it "returns the value for the passed method from the method/value table" do
-    os = OpenStruct.new(age: 20)
-    os.method_missing(:age).should eql(20)
-    os.method_missing(:name).should be_nil
-  end
-end