diff --git a/src/prolog/lib/dif.pl b/src/prolog/lib/dif.pl
index 5b6ba1c3..4bb44c0d 100644
--- a/src/prolog/lib/dif.pl
+++ b/src/prolog/lib/dif.pl
@@ -1,4 +1,4 @@
-[:- module(dif, [dif/2]).
+:- module(dif, [dif/2]).
 
 :- use_module(library(atts)).
 :- use_module(library(control), [(\=)/2]).