diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index f91261bf9c5532edb07b85a1919834a9e5be2242..ed4f0162b041bd408b3c041ca3452eccaafaa9e6 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -8881,8 +8881,8 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 		ast_codec_choose(&p->prefs, p->jointcaps, 1, &tmp_fmt);
 
 		ast_format_cap_set(p->owner->nativeformats, &tmp_fmt);
-		ast_format_cap_joint_copy(p->caps, vpeercapability, p->owner->nativeformats);
-		ast_format_cap_joint_copy(p->caps, tpeercapability, p->owner->nativeformats);
+		ast_format_cap_joint_append(p->caps, vpeercapability, p->owner->nativeformats);
+		ast_format_cap_joint_append(p->caps, tpeercapability, p->owner->nativeformats);
 
 		ast_set_read_format(p->owner, &p->owner->readformat);
 		ast_set_write_format(p->owner, &p->owner->writeformat);
diff --git a/include/asterisk/format_cap.h b/include/asterisk/format_cap.h
index 301ec1471e442368bfe1544ac0a028cb517319b0..cdb5421f9be047cf89954dcf99a3d84b662b52fa 100644
--- a/include/asterisk/format_cap.h
+++ b/include/asterisk/format_cap.h
@@ -191,6 +191,14 @@ struct ast_format_cap *ast_format_cap_joint(const struct ast_format_cap *cap1, c
  */
 int ast_format_cap_joint_copy(const struct ast_format_cap *cap1, const struct ast_format_cap *cap2, struct ast_format_cap *result);
 
+/*!
+ * \brief Get joint capability structure, append into result capabilities structure
+ *
+ * \retval 1, joint capabilities exist
+ * \retval 0, joint capabilities do not exist
+ */
+int ast_format_cap_joint_append(const struct ast_format_cap *cap1, const struct ast_format_cap *cap2, struct ast_format_cap *result);
+
 /*!
  * \brief Find out if capability structures have any joint capabilities without
  * returning those capabilities.
diff --git a/main/format_cap.c b/main/format_cap.c
index 1d566050f7fd22372e97be9d0ff7f31c3bb12b84..c8bdd4fa34616eea271e068836683a4a7c6595f4 100644
--- a/main/format_cap.c
+++ b/main/format_cap.c
@@ -409,7 +409,7 @@ struct ast_format_cap *ast_format_cap_joint(const struct ast_format_cap *cap1, c
 	return NULL;
 }
 
-int ast_format_cap_joint_copy(const struct ast_format_cap *cap1, const struct ast_format_cap *cap2, struct ast_format_cap *result)
+static int joint_copy_helper(const struct ast_format_cap *cap1, const struct ast_format_cap *cap2, struct ast_format_cap *result, int append)
 {
 	struct ao2_iterator it;
 	struct ast_format *tmp;
@@ -417,8 +417,9 @@ int ast_format_cap_joint_copy(const struct ast_format_cap *cap1, const struct as
 		.joint_cap = result,
 		.joint_found = 0,
 	};
-
-	ast_format_cap_remove_all(result);
+	if (!append) {
+		ast_format_cap_remove_all(result);
+	}
 	it = ao2_iterator_init(cap1->formats, cap2->nolock ? AO2_ITERATOR_DONTLOCK : 0);
 	while ((tmp = ao2_iterator_next(&it))) {
 		data.format = tmp;
@@ -433,6 +434,16 @@ int ast_format_cap_joint_copy(const struct ast_format_cap *cap1, const struct as
 	return ao2_container_count(result->formats) ? 1 : 0;
 }
 
+int ast_format_cap_joint_append(const struct ast_format_cap *cap1, const struct ast_format_cap *cap2, struct ast_format_cap *result)
+{
+	return joint_copy_helper(cap1, cap2, result, 1);
+}
+
+int ast_format_cap_joint_copy(const struct ast_format_cap *cap1, const struct ast_format_cap *cap2, struct ast_format_cap *result)
+{
+	return joint_copy_helper(cap1, cap2, result, 0);
+}
+
 struct ast_format_cap *ast_format_cap_get_type(const struct ast_format_cap *cap, enum ast_format_type ftype)
 {
 	struct ao2_iterator it;