diff --git a/p2p/base/connection.h b/p2p/base/connection.h
index 9f3ad21125..0ce2b5d615 100644
--- a/p2p/base/connection.h
+++ b/p2p/base/connection.h
@@ -86,7 +86,7 @@ class Connection : public CandidatePairInterface,
   ~Connection() override;
 
   // A unique ID assigned when the connection is created.
-  uint32_t id() { return id_; }
+  uint32_t id() const { return id_; }
 
   // Implementation of virtual methods in CandidatePairInterface.
   // Returns the description of the local port