diff --git a/src/internet-stack/ipv4-l3-protocol.h b/src/internet-stack/ipv4-l3-protocol.h
index f4b44758c..31f8c3d55 100644
--- a/src/internet-stack/ipv4-l3-protocol.h
+++ b/src/internet-stack/ipv4-l3-protocol.h
@@ -45,7 +45,6 @@ class Node;
 class Socket;
 class Ipv4RawSocketImpl;
 class Ipv4L4Protocol;
-class Ipv4L4Protocol;
 class Icmpv4L4Protocol;