diff --git a/src/stkutil.c b/src/stkutil.c
index a945ef32..2efd25a8 100644
--- a/src/stkutil.c
+++ b/src/stkutil.c
@@ -5055,6 +5055,16 @@ const unsigned char *stk_pdu_from_envelope(const struct stk_envelope *envelope,
 					&envelope->timer_expiration.value,
 					NULL);
 		break;
+	case STK_ENVELOPE_TYPE_USSD_DOWNLOAD:
+		ok = build_dataobj(&builder,
+					build_envelope_dataobj_device_ids,
+					DATAOBJ_FLAG_CR,
+					envelope,
+					build_dataobj_ussd_string,
+					DATAOBJ_FLAG_CR,
+					&envelope->ussd_data_download.string,
+					NULL);
+		break;
 	default:
 		return NULL;
 	};
diff --git a/src/stkutil.h b/src/stkutil.h
index baeaedbd..74ec6009 100644
--- a/src/stkutil.h
+++ b/src/stkutil.h
@@ -1433,6 +1433,10 @@ struct stk_envelope_timer_expiration {
 	struct stk_timer_value value;
 };
 
+struct stk_envelope_ussd_data_download {
+	struct stk_ussd_string string;
+};
+
 struct stk_envelope {
 	enum stk_envelope_type type;
 	enum stk_device_identity_type src;
@@ -1445,6 +1449,7 @@ struct stk_envelope {
 		struct stk_envelope_sms_mo_control sms_mo_control;
 		struct stk_envelope_event_download event_download;
 		struct stk_envelope_timer_expiration timer_expiration;
+		struct stk_envelope_ussd_data_download ussd_data_download;
 	};
 };