diff --git a/src/ipc/lowlevel.cr b/src/ipc/lowlevel.cr
index 119ef30..aeceabf 100644
--- a/src/ipc/lowlevel.cr
+++ b/src/ipc/lowlevel.cr
@@ -31,6 +31,10 @@ lib LibIPC
 	struct Switching
 		origin : LibC::Int
 		dest :   LibC::Int
+		orig_cb_in  : (fd : Int32, Pointer(Message)) -> ConnectionType
+		orig_cb_out : (fd : Int32, Pointer(Message)) -> ConnectionType
+		dest_cb_in  : (fd : Int32, Pointer(Message)) -> ConnectionType
+		dest_cb_out : (fd : Int32, Pointer(Message)) -> ConnectionType
 	end
 
 	struct Switchings