diff --git a/lib/oga/xpath/compiler.rb b/lib/oga/xpath/compiler.rb
index 5f1327b..6f65c8c 100644
--- a/lib/oga/xpath/compiler.rb
+++ b/lib/oga/xpath/compiler.rb
@@ -192,6 +192,21 @@ module Oga
         self_test.followed_by(ancestors_test)
       end
 
+      ##
+      # Processes the `ancestor` axis.
+      #
+      # @param [AST::Node] ast
+      # @param [Oga::Ruby::Node] input
+      # @return [Oga::Ruby::Node]
+      #
+      def on_axis_ancestor(ast, input, &block)
+        parent = literal('parent')
+
+        input.each_ancestor.add_block(parent) do
+          process(ast, parent, &block).if_true { yield parent }
+        end
+      end
+
       ##
       # Processes a node test predicate.
       #
diff --git a/spec/oga/xpath/compiler/axes/ancestor_spec.rb b/spec/oga/xpath/compiler/axes/ancestor_spec.rb
index bcffee7..5772ba3 100644
--- a/spec/oga/xpath/compiler/axes/ancestor_spec.rb
+++ b/spec/oga/xpath/compiler/axes/ancestor_spec.rb
@@ -22,6 +22,10 @@ describe Oga::XPath::Compiler do
       evaluate_xpath(@c1, 'ancestor::*[1]').should == node_set(@b1)
     end
 
+    it 'returns a node set containing all ancestors' do
+      evaluate_xpath(@c1, 'ancestor::*').should == node_set(@b1, @a1)
+    end
+
     it 'returns an empty node set for non existing ancestors' do
       evaluate_xpath(@c1, 'ancestor::c').should == node_set
     end