diff --git a/include/types/pattern.h b/include/types/pattern.h
index 3859edab9..fa29274c7 100644
--- a/include/types/pattern.h
+++ b/include/types/pattern.h
@@ -220,7 +220,7 @@ extern char *pat_match_names[PAT_MATCH_NUM];
 extern int (*pat_parse_fcts[PAT_MATCH_NUM])(const char *, struct pattern *, char **);
 extern int (*pat_index_fcts[PAT_MATCH_NUM])(struct pattern_expr *, struct pattern *, char **);
 extern void (*pat_delete_fcts[PAT_MATCH_NUM])(struct pattern_expr *, struct pat_ref_elt *);
-void (*pat_prune_fcts[PAT_MATCH_NUM])(struct pattern_expr *);
+extern void (*pat_prune_fcts[PAT_MATCH_NUM])(struct pattern_expr *);
 extern struct pattern *(*pat_match_fcts[PAT_MATCH_NUM])(struct sample *, struct pattern_expr *, int);
 extern int pat_match_types[PAT_MATCH_NUM];