diff --git a/cpu/avr8_common/include/cpu.h b/cpu/avr8_common/include/cpu.h
index 42cfd34354..3e221584d6 100644
--- a/cpu/avr8_common/include/cpu.h
+++ b/cpu/avr8_common/include/cpu.h
@@ -63,6 +63,11 @@ extern "C"
 #define AVR8_STATE_FLAG_ISR           (0x80U) /**< In ISR */
 #define AVR8_STATE_FLAG_UART0_TX      (0x01U) /**< TX pending for UART 0 */
 #define AVR8_STATE_FLAG_UART1_TX      (0x02U) /**< TX pending for UART 1 */
+#define AVR8_STATE_FLAG_UART2_TX      (0x04U) /**< TX pending for UART 2 */
+#define AVR8_STATE_FLAG_UART3_TX      (0x08U) /**< TX pending for UART 3 */
+#define AVR8_STATE_FLAG_UART4_TX      (0x10U) /**< TX pending for UART 4 */
+#define AVR8_STATE_FLAG_UART5_TX      (0x20U) /**< TX pending for UART 5 */
+#define AVR8_STATE_FLAG_UART6_TX      (0x40U) /**< TX pending for UART 6 */
 #define AVR8_STATE_FLAG_UART_TX(x)    (0x01U << x) /**< TX pending for UART x */
 /** @} */
 
@@ -77,14 +82,18 @@ extern "C"
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *   7   6   5   4   3   2   1   0
  * +---+---+---+---+---+---+---+---+
- * |IRQ| unused            |TX1|TX0|
+ * |IRQ|TX6|TX5|TX4|TX3|TX2|TX1|TX0|
  * +---+---+---+---+---+---+---+---+
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *
  * | Label  | Description                                                   |
  * |:-------|:--------------------------------------------------------------|
  * | IRQ    | This bit is set when in IRQ context                           |
- * | unused | This bits are currently not used                              |
+ * | TX6    | This bit is set when on UART6 TX is pending                   |
+ * | TX5    | This bit is set when on UART5 TX is pending                   |
+ * | TX4    | This bit is set when on UART4 TX is pending                   |
+ * | TX3    | This bit is set when on UART3 TX is pending                   |
+ * | TX2    | This bit is set when on UART2 TX is pending                   |
  * | TX1    | This bit is set when on UART1 TX is pending                   |
  * | TX0    | This bit is set when on UART0 TX is pending                   |
  */
@@ -138,7 +147,13 @@ static inline void avr8_enter_isr(void)
 static inline int avr8_is_uart_tx_pending(void)
 {
     uint8_t state = avr8_get_state();
-    return (state & (AVR8_STATE_FLAG_UART0_TX | AVR8_STATE_FLAG_UART1_TX));
+    return (state & (AVR8_STATE_FLAG_UART0_TX
+                  |  AVR8_STATE_FLAG_UART1_TX
+                  |  AVR8_STATE_FLAG_UART2_TX
+                  |  AVR8_STATE_FLAG_UART3_TX
+                  |  AVR8_STATE_FLAG_UART4_TX
+                  |  AVR8_STATE_FLAG_UART5_TX
+                  |  AVR8_STATE_FLAG_UART6_TX));
 }
 
 /**