diff --git a/CMakeLists.txt b/CMakeLists.txt
index a9816e8..58cdf70 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,11 @@ project(nuki_hub CXX)
 
 set(LOG_LEVEL ARDUHAL_LOG_LEVEL_NONE)
 
+# Length of char arrays to store certificates for MQTTS
+add_compile_definitions(TLS_CA_MAX_SIZE=1800)
+add_compile_definitions(TLS_CERT_MAX_SIZE=1800)
+add_compile_definitions(TLS_KEY_MAX_SIZE=1800)
+
 include_directories(${PROJECT_NAME}
         PRIVATE
         lib/Crc16
diff --git a/WebCfgServer.cpp b/WebCfgServer.cpp
index af24b06..8cec783 100644
--- a/WebCfgServer.cpp
+++ b/WebCfgServer.cpp
@@ -452,9 +452,9 @@ void WebCfgServer::buildMqttConfigHtml(String &response)
     printInputField(response, "MQTTPORT", "MQTT Broker port", _preferences->getInt(preference_mqtt_broker_port), 5);
     printInputField(response, "MQTTUSER", "MQTT User (# to clear)", _preferences->getString(preference_mqtt_user).c_str(), 30);
     printInputField(response, "MQTTPASS", "MQTT Password", "*", 30, true);
-    printTextarea(response, "MQTTCA", "MQTT SSL CA Certificate", _preferences->getString(preference_mqtt_ca).c_str(), 1800);
-    printTextarea(response, "MQTTCRT", "MQTT SSL Client Certificate", _preferences->getString(preference_mqtt_crt).c_str(), 1800);
-    printTextarea(response, "MQTTKEY", "MQTT SSL Client Key", _preferences->getString(preference_mqtt_key).c_str(), 1800);
+    printTextarea(response, "MQTTCA", "MQTT SSL CA Certificate", _preferences->getString(preference_mqtt_ca).c_str(), TLS_CA_MAX_SIZE);
+    printTextarea(response, "MQTTCRT", "MQTT SSL Client Certificate", _preferences->getString(preference_mqtt_crt).c_str(), TLS_CERT_MAX_SIZE);
+    printTextarea(response, "MQTTKEY", "MQTT SSL Client Key", _preferences->getString(preference_mqtt_key).c_str(), TLS_KEY_MAX_SIZE);
     printInputField(response, "NETTIMEOUT", "Network Timeout until restart (seconds; -1 to disable)", _preferences->getInt(preference_network_timeout), 5);
     response.concat("</table>");
     response.concat("<br><INPUT TYPE=SUBMIT NAME=\"submit\" VALUE=\"Save\">");
diff --git a/networkDevices/WifiDevice.h b/networkDevices/WifiDevice.h
index ec1ed1e..8f2e522 100644
--- a/networkDevices/WifiDevice.h
+++ b/networkDevices/WifiDevice.h
@@ -6,10 +6,6 @@
 #include "NetworkDevice.h"
 #include "../SpiffsCookie.h"
 
-#define TLS_CA_MAX_SIZE 1800
-#define TLS_CERT_MAX_SIZE 1800
-#define TLS_KEY_MAX_SIZE 1800
-
 class WifiDevice : public NetworkDevice
 {
 public: