3 files changed, 21 insertions, 0 deletions
diff --git a/spec/ruby/optional/capi/ext/module_spec.c b/spec/ruby/optional/capi/ext/module_spec.c
index 275bc4da32..e408404a09 100644
--- a/spec/ruby/optional/capi/ext/module_spec.c
+++ b/spec/ruby/optional/capi/ext/module_spec.c
@@ -152,6 +152,12 @@ static VALUE module_specs_rbclass2name(VALUE self, VALUE klass) {
 }
 #endif
 
+#ifdef HAVE_RB_MOD_ANCESTORS
+static VALUE module_specs_rb_mod_ancestors(VALUE self, VALUE klass) {
+  return rb_mod_ancestors(klass);
+}
+#endif
+
 void Init_module_spec(void) {
   VALUE cls;
 
@@ -245,6 +251,10 @@ void Init_module_spec(void) {
 #ifdef HAVE_RB_CLASS2NAME
   rb_define_method(cls, "rb_class2name", module_specs_rbclass2name, 1);
 #endif
+
+#ifdef HAVE_RB_MOD_ANCESTORS
+  rb_define_method(cls, "rb_mod_ancestors", module_specs_rb_mod_ancestors, 1);
+#endif
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/rubyspec.h b/spec/ruby/optional/capi/ext/rubyspec.h
index 8866e39af4..12c71d98b0 100644
--- a/spec/ruby/optional/capi/ext/rubyspec.h
+++ b/spec/ruby/optional/capi/ext/rubyspec.h
@@ -401,6 +401,7 @@
 #define HAVE_RB_DEFINE_PRIVATE_METHOD      1
 #define HAVE_RB_DEFINE_PROTECTED_METHOD    1
 #define HAVE_RB_DEFINE_SINGLETON_METHOD    1
+#define HAVE_RB_MOD_ANCESTORS              1
 #define HAVE_RB_UNDEF                      1
 #define HAVE_RB_UNDEF_METHOD               1
 
diff --git a/spec/ruby/optional/capi/module_spec.rb b/spec/ruby/optional/capi/module_spec.rb
index 23fb674f0e..b3aeae4011 100644
--- a/spec/ruby/optional/capi/module_spec.rb
+++ b/spec/ruby/optional/capi/module_spec.rb
@@ -339,4 +339,14 @@ describe "CApiModule" do
       @m.rb_class2name(CApiModuleSpecs::M).should == "CApiModuleSpecs::M"
     end
   end
+
+  describe "rb_mod_ancestors" do
+    it "returns an array of ancestors" do
+      one = Module.new
+      two = Module.new do
+        include one
+      end
+      @m.rb_mod_ancestors(two).should == [two, one]
+    end
+  end
 end