diff --git a/doc/README.heuristic b/doc/README.heuristic
index 1746bd97ee..e554d505f9 100644
--- a/doc/README.heuristic
+++ b/doc/README.heuristic
@@ -122,7 +122,7 @@ dissect_PROTOABBREV(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *d
 
 
 static gboolean
-dissect_PROTOABBREV_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
+dissect_PROTOABBREV_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
 {
 ...