diff --git a/mqttpacket.cpp b/mqttpacket.cpp
index 635dd5f..c11cb99 100644
--- a/mqttpacket.cpp
+++ b/mqttpacket.cpp
@@ -63,6 +63,11 @@ MqttPacket::MqttPacket(const SubAck &subAck) :
     first_byte = static_cast<char>(packetType) << 4;
     writeUint16(subAck.packet_id);
 
+    if (subAck.protocol_version >= ProtocolVersion::Mqtt5)
+    {
+        writeProperties(subAck.propertyBuilder);
+    }
+
     std::vector<char> returnList;
     for (SubAckReturnCodes code : subAck.responses)
     {
@@ -665,7 +670,7 @@ void MqttPacket::handleSubscribe()
         throw ProtocolError("No topics specified to subscribe to.");
     }
 
-    SubAck subAck(packet_id, subs_reponse_codes);
+    SubAck subAck(this->protocolVersion, packet_id, subs_reponse_codes);
     MqttPacket response(subAck);
     sender->writeMqttPacket(response);
 }
diff --git a/types.cpp b/types.cpp
index b4ea0a0..0b46019 100644
--- a/types.cpp
+++ b/types.cpp
@@ -82,7 +82,8 @@ size_t ConnAck::getLengthWithoutFixedHeader() const
     return result;
 }
 
-SubAck::SubAck(uint16_t packet_id, const std::list<char> &subs_qos_reponses) :
+SubAck::SubAck(const ProtocolVersion protVersion, uint16_t packet_id, const std::list<char> &subs_qos_reponses) :
+    protocol_version(protVersion),
     packet_id(packet_id)
 {
     assert(!subs_qos_reponses.empty());
@@ -97,6 +98,12 @@ size_t SubAck::getLengthWithoutFixedHeader() const
 {
     size_t result = responses.size();
     result += 2; // Packet ID
+
+    if (this->protocol_version >= ProtocolVersion::Mqtt5)
+    {
+        const size_t proplen = propertyBuilder ? propertyBuilder->getLength() : 1;
+        result += proplen;
+    }
     return result;
 }
 
diff --git a/types.h b/types.h
index 6875c55..4cf71ac 100644
--- a/types.h
+++ b/types.h
@@ -175,9 +175,12 @@ enum class SubAckReturnCodes
 class SubAck
 {
 public:
+    const ProtocolVersion protocol_version;
     uint16_t packet_id;
     std::list<SubAckReturnCodes> responses;
-    SubAck(uint16_t packet_id, const std::list<char> &subs_qos_reponses);
+    std::shared_ptr<Mqtt5PropertyBuilder> propertyBuilder;
+
+    SubAck(const ProtocolVersion protVersion, uint16_t packet_id, const std::list<char> &subs_qos_reponses);
     size_t getLengthWithoutFixedHeader() const;
 };