diff --git a/cpu/samd21/include/samd21.h b/cpu/samd21/include/samd21.h
index 805b01e76efe230f87d50a6c24c61b43fb08b0f1..2bbbe5afa089d3281710333ce9438d72d4ced3cc 100644
--- a/cpu/samd21/include/samd21.h
+++ b/cpu/samd21/include/samd21.h
@@ -227,7 +227,9 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
+#ifndef LITTLE_ENDIAN
+#   define LITTLE_ENDIAN       1
+#endif
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */