diff --git a/boards/nucleo-l152/include/periph_conf.h b/boards/nucleo-l152/include/periph_conf.h
index 7a08df35ba..5285511628 100644
--- a/boards/nucleo-l152/include/periph_conf.h
+++ b/boards/nucleo-l152/include/periph_conf.h
@@ -32,6 +32,9 @@ extern "C" {
  **/
 #define CLOCK_HSI           (16000000U)             /* frequency of internal oscillator */
 #define CLOCK_CORECLOCK     (32000000U)             /* targeted core clock frequency */
+/* 0: no external low speed crystal available,
+ * 1: external crystal available (always 32.768kHz) */
+#define CLOCK_LSE           (1)
 /* configuration of PLL prescaler and multiply values */
 /* CORECLOCK := HSI / CLOCK_PLL_DIV * CLOCK_PLL_MUL */
 #define CLOCK_PLL_DIV       RCC_CFGR_PLLDIV2