diff --git a/boards/microbit/include/periph_conf.h b/boards/microbit/include/periph_conf.h
index 5079f243b..4cca5c2af 100644
--- a/boards/microbit/include/periph_conf.h
+++ b/boards/microbit/include/periph_conf.h
@@ -33,7 +33,7 @@ extern "C" {
  * @{
  */
 #define CLOCK_CORECLOCK     (16000000U)     /* fixed for all NRF51822 */
-#define CLOCK_CRYSTAL       (0U)            /* set to  0: internal RC oscillator
+#define CLOCK_CRYSTAL       (16U)           /* set to  0: internal RC oscillator
                                                       16: 16MHz crystal
                                                       32: 32MHz crystal */
 /** @} */