diff --git a/src/adjacent.hpp b/src/adjacent.hpp
index 499e45e..dcdefc8 100644
--- a/src/adjacent.hpp
+++ b/src/adjacent.hpp
@@ -130,6 +130,15 @@
   bool
   operator==(const Adjacent& adjacent) const;
 
+  bool
+  operator!=(const Adjacent& adjacent) const
+  {
+    return !(*this == adjacent);
+  }
+
+  bool
+  operator<(const Adjacent& adjacent) const;
+
   inline bool
   compare(const ndn::Name& adjacencyName)
   {
@@ -168,8 +177,14 @@
   /*! m_faceId The NFD-assigned ID for the neighbor, used to
    * determine whether a Face is available */
   uint64_t m_faceId;
+
+  friend std::ostream&
+  operator<<(std::ostream& os, const Adjacent& adjacent);
 };
 
+std::ostream&
+operator<<(std::ostream& os, const Adjacent& adjacent);
+
 } // namespace nlsr
 
 #endif // NLSR_ADJACENT_HPP