Skip node matching for incompatible nodes.

lib/oga/xpath/evaluator.rb

@@ -107,7 +107,9 @@ module Oga
         nodes = XML::NodeSet.new
 
         context.each do |xml_node|
-          nodes << xml_node if node_matches?(xml_node, node)
+          if can_match_node?(xml_node) and node_matches?(xml_node, node)
+            nodes << xml_node
+          end
         end
 
         return nodes
@@ -259,6 +261,16 @@ module Oga
         return name_matches && ns_matches
       end
 
+      ##
+      # Returns `true` if the given XML node can be compared using
+      # {#node_matches?}.
+      #
+      # @param [Oga::XML::Node] node
+      #
+      def can_match_node?(node)
+        return node.respond_to?(:name) && node.respond_to?(:namespace)
+      end
+
       ##
       # @param [Oga::XML::Node] node
       # @return [TrueClass|FalseClass]

spec/oga/xpath/evaluator/paths_spec.rb

@@ -2,7 +2,7 @@ require 'spec_helper'
 
 describe Oga::XPath::Evaluator do
   before do
-    @document  = parse('<a><b></b><b></b><ns1:c></ns1:c></a>')
+    @document  = parse('<a>Foo<b></b><b></b><ns1:c></ns1:c></a>')
     @evaluator = described_class.new(@document)
   end
 
@@ -56,8 +56,8 @@ describe Oga::XPath::Evaluator do
     example 'return the correct nodes' do
       a = @document.children[0]
 
-      @set[0].should == a.children[0]
+      @set[0].should == a.children[1]
-      @set[1].should == a.children[1]
+      @set[1].should == a.children[2]
     end
   end