diff --git a/firmware/firmware.ino b/firmware/firmware.ino
index 4dbd9cb..831474b 100644
--- a/firmware/firmware.ino
+++ b/firmware/firmware.ino
@@ -8,6 +8,10 @@
 #include <Ticker.h>
 #include <time.h>
 
+#if !defined(ARDUINO_ESP8266_RELEASE_2_5_0) || ARDUINOJSON_VERSION_MAJOR != 5 || ARDUINOJSON_VERSION_MINOR != 13 || ARDUINOJSON_VERSION_REVISION != 3
+#error Incorrect library version detected. See README.
+#endif
+
 const char *FIRMWARE_VERSION = "MRWIZARD 0010 MRWIZARD";
 
 const char *WIFI_SSID PROGMEM = "Protospace";