diff --git a/README.md b/README.md
index 623f5ca..3585b72 100644
--- a/README.md
+++ b/README.md
@@ -6,10 +6,12 @@
 
 ## Compatible Arduino Shields
 
-## Roadmap
+## Supported types
 
-- [ ] Add support for "Lights" device's type
-- [ ] Add support for "Sensor" device's type
-- [ ] Add support for "Tag scanner" device's type
-- [ ] Add support for "Lock" device's type
-- [ ] Add support for "Binary sensor" device's type
+- :heavy_check_mark: Binary sensors
+- :heavy_check_mark: Device triggers
+- :heavy_check_mark: Switches
+- :heavy_check_mark: Sensors
+- :heavy_check_mark: Tag scanners
+
+If you need support for non-listed device's type please open a new issue in the Github repository.
diff --git a/src/HAMqtt.cpp b/src/HAMqtt.cpp
index 38718b1..66de182 100644
--- a/src/HAMqtt.cpp
+++ b/src/HAMqtt.cpp
@@ -6,7 +6,7 @@
 #include "ArduinoHADefines.h"
 #include "device-types/BaseDeviceType.h"
 
-const char* HAMqtt::DefaultDiscoveryPrefix = "homeassistant";
+static const char DefaultDiscoveryPrefix[] PROGMEM = {"homeassistant"};
 HAMqtt* instance = nullptr;
 
 void onMessageReceived(char* topic, uint8_t* payload, uint16_t length)
@@ -24,7 +24,6 @@ HAMqtt::HAMqtt(const char* clientId, Client& netClient, HADevice& device) :
     _device(device),
     _hasDevice(true),
     _initialized(false),
-    _discoveryPrefix(DefaultDiscoveryPrefix),
     _mqtt(new PubSubClient(netClient)),
     _serverIp(new IPAddress()),
     _serverPort(0),
@@ -35,6 +34,7 @@ HAMqtt::HAMqtt(const char* clientId, Client& netClient, HADevice& device) :
     _devicesTypes(nullptr)
 {
     instance = this;
+    strcpy_P(_discoveryPrefix, DefaultDiscoveryPrefix);
 }
 
 bool HAMqtt::begin(
diff --git a/src/HAMqtt.h b/src/HAMqtt.h
index bd6a426..cc37605 100644
--- a/src/HAMqtt.h
+++ b/src/HAMqtt.h
@@ -12,7 +12,6 @@ class BaseDeviceType;
 class HAMqtt
 {
 public:
-    static const char* DefaultDiscoveryPrefix;
     static const uint16_t ReconnectInterval = 3000; // ms
 
     HAMqtt(const char* clientId, Client& netClient, HADevice& device);