diff --git a/include/haproxy/pattern.h b/include/haproxy/pattern.h
index db0a8a32f..159eca18b 100644
--- a/include/haproxy/pattern.h
+++ b/include/haproxy/pattern.h
@@ -190,6 +190,7 @@ int pat_ref_push(struct pat_ref_elt *elt, struct pattern_expr *expr, int patflag
 int pat_ref_add(struct pat_ref *ref, const char *pattern, const char *sample, char **err);
 int pat_ref_set(struct pat_ref *ref, const char *pattern, const char *sample, char **err);
 int pat_ref_set_elt_duplicate(struct pat_ref *ref, struct pat_ref_elt *elt, const char *value, char **err);
+int pat_ref_gen_set(struct pat_ref *ref, unsigned int gen_id, const char *key, const char *value, char **err);
 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);
 void pat_ref_delete_by_ptr(struct pat_ref *ref, struct pat_ref_elt *elt);
diff --git a/src/pattern.c b/src/pattern.c
index e8e995deb..01f27b669 100644
--- a/src/pattern.c
+++ b/src/pattern.c
@@ -1788,6 +1788,26 @@ int pat_ref_set_elt_duplicate(struct pat_ref *ref, struct pat_ref_elt *elt, cons
 	return pat_ref_set_from_node(ref, &elt->node, value, err);
 }
 
+/* This function modifies to <value> the sample of all patterns matching <key>
+ * and belonging to <gen_id> under <ref>.
+ */
+int pat_ref_gen_set(struct pat_ref *ref, unsigned int gen_id,
+                    const char *key, const char *value, char **err)
+{
+	struct ebmb_node *node;
+	struct pat_ref_elt *elt;
+
+	/* Look for pattern in the reference. */
+	node = ebst_lookup(&ref->ebmb_root, key);
+	while (node) {
+		elt = ebmb_entry(node, struct pat_ref_elt, node);
+		if (elt->gen_id == gen_id)
+			break;
+		node = ebmb_next_dup(node);
+	}
+	return pat_ref_set_from_node(ref, node, value, err);
+}
+
 /* This function modifies to <value> the sample of all patterns matching <key>
  * under <ref>.
  */