diff --git a/lib/sdoc/rdoc_monkey_patches.rb b/lib/sdoc/rdoc_monkey_patches.rb
index ce858e5e..146df850 100644
--- a/lib/sdoc/rdoc_monkey_patches.rb
+++ b/lib/sdoc/rdoc_monkey_patches.rb
@@ -60,3 +60,15 @@ def record_location(*)
     super unless @ignoring_constants
   end
 end)
+
+RDoc::Markup::PreProcess.prepend(Module.new do
+  def find_include_file(name)
+    to_search = [File.dirname(@input_file_name, 2)].concat @include_path
+    to_search.each do |dir|
+      full_name = File.join(dir, name)
+      stat = File.stat(full_name) rescue next
+      return full_name if stat.readable?
+    end
+    nil
+  end
+end)
diff --git a/spec/rdoc_monkey_patches_spec.rb b/spec/rdoc_monkey_patches_spec.rb
index bd980c52..c7b3d373 100644
--- a/spec/rdoc_monkey_patches_spec.rb
+++ b/spec/rdoc_monkey_patches_spec.rb
@@ -114,4 +114,28 @@ def foo; Float::INFINITY; end
       end
     end
   end
+
+  describe RDoc::Markup::PreProcess do
+    it "includes files relative to the framework root" do
+      Dir.mktmpdir do |dir|
+        Dir.chdir(dir) do
+          FileUtils.mkdir_p("railties/lib")
+          File.write("railties/lib/rails.rb", <<~RUBY)
+            # :include: README.md
+            module Rails
+            end
+          RUBY
+
+          File.write("railties/README.md", <<~RUBY)
+            Railties - Gluing the Engine to the Rails
+          RUBY
+
+          rdoc_store = rdoc_dry_run("--files", "railties/lib/rails.rb", "railties/README.md").store
+
+          _(rdoc_store.find_class_or_module("Rails").description).
+            must_match %r"Railties - Gluing the Engine to the Rails"
+        end
+      end
+    end
+  end
 end