diff --git a/include/proto/pattern.h b/include/proto/pattern.h
index 73d3cdc..1480d79 100644
--- a/include/proto/pattern.h
+++ b/include/proto/pattern.h
@@ -191,7 +191,7 @@
 int pat_ref_set_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt, const char *value, char **err);
 int pat_ref_delete(struct pat_ref *ref, const char *key);
 int pat_ref_delete_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt);
-void pat_ref_prune(struct pat_ref *ref);
+int pat_ref_prune(struct pat_ref *ref);
 int pat_ref_load(struct pat_ref *ref, struct pattern_expr *expr, int patflags, int soe, char **err);
 void pat_ref_reload(struct pat_ref *ref, struct pat_ref *replace);