diff --git a/client.cpp b/client.cpp
index 088a9c1..c114f1a 100644
--- a/client.cpp
+++ b/client.cpp
@@ -334,6 +334,25 @@ void Client::resetBuffersIfEligible()
     writebuf.resetSizeIfEligable(initialBufferSize);
 }
 
+void Client::setTopicAlias(const uint16_t alias_id, const std::string &topic)
+{
+    if (alias_id == 0)
+        throw ProtocolError("Client tried to set topic alias 0, which is a protocol error.");
+
+    if (topic.empty())
+        return;
+
+    if (alias_id > this->maxTopicAliases)
+        throw ProtocolError("Client exceeded max topic aliases.");
+
+    this->topicAliases[alias_id] = topic;
+}
+
+const std::string &Client::getTopicAlias(const uint16_t id)
+{
+    return this->topicAliases[id];
+}
+
 #ifndef NDEBUG
 /**
  * @brief IoWrapper::setFakeUpgraded().
diff --git a/client.h b/client.h
index fc397f7..737b64b 100644
--- a/client.h
+++ b/client.h
@@ -82,6 +82,8 @@ class Client
 
     std::shared_ptr<Session> session;
 
+    std::unordered_map<uint16_t, std::string> topicAliases;
+
     Logger *logger = Logger::getInstance();
 
     void setReadyForWriting(bool val);
@@ -137,6 +139,9 @@ public:
     std::string getKeepAliveInfoString() const;
     void resetBuffersIfEligible();
 
+    void setTopicAlias(const uint16_t alias_id, const std::string &topic);
+    const std::string &getTopicAlias(const uint16_t id);
+
 #ifndef NDEBUG
     void setFakeUpgraded();
 #endif
diff --git a/mqttpacket.cpp b/mqttpacket.cpp
index 6864d9f..689bc53 100644
--- a/mqttpacket.cpp
+++ b/mqttpacket.cpp
@@ -343,7 +343,7 @@ void MqttPacket::handleConnect()
         uint16_t max_qos_packets = settings.maxQosMsgPendingPerClient;
         uint32_t session_expire = settings.expireSessionsAfterSeconds > 0 ? settings.expireSessionsAfterSeconds : std::numeric_limits<uint32_t>::max();
         uint32_t max_packet_size = settings.maxPacketSize;
-        uint16_t max_topic_aliases = 0;
+        uint16_t max_topic_aliases = settings.maxTopicAliases;
         bool request_response_information = false;
         bool request_problem_information = false;
 
@@ -750,10 +750,7 @@ void MqttPacket::handleUnsubscribe()
 
 void MqttPacket::handlePublish()
 {
-    uint16_t variable_header_length = readTwoBytesToUInt16();
-
-    if (variable_header_length == 0)
-        throw ProtocolError("Empty publish topic");
+    const uint16_t variable_header_length = readTwoBytesToUInt16();
 
     bool retain = (first_byte & 0b00000001);
     bool dup = !!(first_byte & 0b00001000);
@@ -767,19 +764,6 @@ void MqttPacket::handlePublish()
         throw ProtocolError("Duplicate flag is set for QoS 0 packet. This is illegal.");
 
     publishData.topic = std::string(readBytes(variable_header_length), variable_header_length);
-    splitTopic(publishData.topic, publishData.subtopics);
-
-    if (!isValidUtf8(publishData.topic, true))
-    {
-        logger->logf(LOG_WARNING, "Client '%s' published a message with invalid UTF8 or $/+/# in it. Dropping.", sender->repr().c_str());
-        return;
-    }
-
-#ifndef NDEBUG
-    logger->logf(LOG_DEBUG, "Publish received, topic '%s'. QoS=%d. Retain=%d, dup=%d", publishData.topic.c_str(), qos, retain, dup);
-#endif
-
-    sender->getThreadData()->incrementReceivedMessageCount();
 
     if (qos)
     {
@@ -820,6 +804,7 @@ void MqttPacket::handlePublish()
         const size_t proplen = decodeVariableByteIntAtPos();
         const size_t prop_end_at = pos + proplen;
 
+        // TODO: don't do this when the only properties are expiry and topic alias; they don't need the builder.
         if (proplen > 0)
             publishData.constructPropertyBuilder();
 
@@ -836,7 +821,21 @@ void MqttPacket::handlePublish()
                 publishData.createdAt = std::chrono::steady_clock::now();
                 publishData.expiresAfter = std::chrono::seconds(readFourBytesToUint32());
             case Mqtt5Properties::TopicAlias:
+            {
+                const uint16_t alias_id = readTwoBytesToUInt16();
+                this->hasTopicAlias = true;
+
+                if (publishData.topic.empty())
+                {
+                    publishData.topic = sender->getTopicAlias(alias_id);
+                }
+                else
+                {
+                    sender->setTopicAlias(alias_id, publishData.topic);
+                }
+
                 break;
+            }
             case Mqtt5Properties::ResponseTopic:
             {
                 const uint16_t len = readTwoBytesToUInt16();
@@ -878,6 +877,23 @@ void MqttPacket::handlePublish()
         }
     }
 
+    splitTopic(publishData.topic, publishData.subtopics);
+
+    if (!isValidUtf8(publishData.topic, true))
+    {
+        logger->logf(LOG_WARNING, "Client '%s' published a message with invalid UTF8 or $/+/# in it. Dropping.", sender->repr().c_str());
+        return;
+    }
+
+    if (publishData.topic.empty())
+        throw ProtocolError("Empty publish topic");
+
+#ifndef NDEBUG
+    logger->logf(LOG_DEBUG, "Publish received, topic '%s'. QoS=%d. Retain=%d, dup=%d", publishData.topic.c_str(), qos, retain, dup);
+#endif
+
+    sender->getThreadData()->incrementReceivedMessageCount();
+
     payloadLen = remainingAfterPos();
     payloadStart = pos;
 
@@ -1237,7 +1253,7 @@ bool MqttPacket::containsClientSpecificProperties() const
     if (protocolVersion <= ProtocolVersion::Mqtt311 || !publishData.propertyBuilder)
         return false;
 
-    if (publishData.createdAt.time_since_epoch().count() == 0) // TODO: better
+    if (publishData.createdAt.time_since_epoch().count() == 0 || this->hasTopicAlias) // TODO: better
     {
         return true;
     }
diff --git a/mqttpacket.h b/mqttpacket.h
index 929c8de..5283060 100644
--- a/mqttpacket.h
+++ b/mqttpacket.h
@@ -54,6 +54,7 @@ class MqttPacket
     ProtocolVersion protocolVersion = ProtocolVersion::None;
     size_t payloadStart = 0;
     size_t payloadLen = 0;
+    bool hasTopicAlias = false;
     Logger *logger = Logger::getInstance();
 
     char *readBytes(size_t length);
diff --git a/settings.h b/settings.h
index 6910629..e60c506 100644
--- a/settings.h
+++ b/settings.h
@@ -42,6 +42,7 @@ public:
     bool authPluginSerializeAuthChecks = false;
     int clientInitialBufferSize = 1024; // Must be power of 2
     int maxPacketSize = 268435461; // 256 MB + 5
+    uint16_t maxTopicAliases = 65535;
 #ifdef TESTING
     bool logDebug = true;
 #else