diff --git a/src/knx/tpuart_data_link_layer.cpp b/src/knx/tpuart_data_link_layer.cpp
index 834c212..e74df73 100644
--- a/src/knx/tpuart_data_link_layer.cpp
+++ b/src/knx/tpuart_data_link_layer.cpp
@@ -109,8 +109,6 @@
 #define ACR0_FLAG_TRIGEN 0x08
 #define ACR0_FLAG_V20VCLIMIT 0x04
 
-#define MAX_TX_QUEUE 20
-
 enum
 {
     TX_IDLE,
diff --git a/src/knx/tpuart_data_link_layer.h b/src/knx/tpuart_data_link_layer.h
index 24afa1a..729e7be 100644
--- a/src/knx/tpuart_data_link_layer.h
+++ b/src/knx/tpuart_data_link_layer.h
@@ -8,10 +8,15 @@
 #include <stdint.h>
 
 #define MAX_KNX_TELEGRAM_SIZE 263
+
 #ifndef MAX_RX_QUEUE_BYTES
 #define MAX_RX_QUEUE_BYTES MAX_KNX_TELEGRAM_SIZE + 50
 #endif
 
+#ifndef MAX_TX_QUEUE
+#define MAX_TX_QUEUE 50
+#endif
+
 // __time_critical_func fallback
 #ifndef ARDUINO_ARCH_RP2040
 #define __time_critical_func(X) X