diff --git a/model/pit/ndn-pit-entry-incoming-face.h b/model/pit/ndn-pit-entry-incoming-face.h
index 4597f58..14885c8 100644
--- a/model/pit/ndn-pit-entry-incoming-face.h
+++ b/model/pit/ndn-pit-entry-incoming-face.h
@@ -60,12 +60,12 @@
   /**
    * @brief Compare two PitEntryIncomingFace
    */
-  bool operator== (const IncomingFace &dst) { return *m_face==*(dst.m_face); }
+  bool operator== (const IncomingFace &dst) const { return *m_face==*(dst.m_face); }
 
   /**
    * @brief Compare PitEntryIncomingFace with Face
    */
-  bool operator== (Ptr<Face> face) { return *m_face==*face; }
+  bool operator== (Ptr<Face> face) const { return *m_face==*face; }
 
   /**
    * \brief Comparison operator used by boost::multi_index::identity<>