diff --git a/lib/liquid/condition.rb b/lib/liquid/condition.rb
index 69224ab..ade7ac1 100644
--- a/lib/liquid/condition.rb
+++ b/lib/liquid/condition.rb
@@ -15,7 +15,7 @@ module Liquid
       '>'  => :>,
       '>=' => :>=,
       '<=' => :<=,
-      'contains' => lambda { |cond, left, right| left.include?(right) },
+      'contains' => lambda { |cond, left, right| left && right ? left.include?(right) : false }
     }
 
     def self.operators
diff --git a/test/condition_test.rb b/test/condition_test.rb
index 7739bd9..0a45482 100644
--- a/test/condition_test.rb
+++ b/test/condition_test.rb
@@ -60,6 +60,12 @@ class ConditionTest < Test::Unit::TestCase
     
   end  
 
+  def test_contains_returns_false_for_nil_operands
+    @context = Liquid::Context.new
+    assert_evalutes_false "not_assigned", 'contains', '0'
+    assert_evalutes_false "0", 'contains', 'not_assigned'
+  end  
+
   def test_or_condition     
     condition = Condition.new('1', '==', '2')