diff --git a/Userland/Libraries/LibIPC/Encoder.h b/Userland/Libraries/LibIPC/Encoder.h
index 5da7b9ac7c..058b33831e 100644
--- a/Userland/Libraries/LibIPC/Encoder.h
+++ b/Userland/Libraries/LibIPC/Encoder.h
@@ -16,7 +16,7 @@
 namespace IPC {
 
 template<typename T>
-bool encode(Encoder&, T&)
+bool encode(Encoder&, T const&)
 {
     static_assert(DependentFalse<T>, "Base IPC::encode() was instantiated");
     VERIFY_NOT_REACHED();
diff --git a/Userland/Libraries/LibIPC/Forward.h b/Userland/Libraries/LibIPC/Forward.h
index ccdb977edb..c59cca64d3 100644
--- a/Userland/Libraries/LibIPC/Forward.h
+++ b/Userland/Libraries/LibIPC/Forward.h
@@ -15,4 +15,10 @@ class Message;
 class File;
 class Stub;
 
+template<typename T>
+bool encode(Encoder&, T const&);
+
+template<typename T>
+ErrorOr<void> decode(Decoder&, T&);
+
 }