diff --git a/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51.c b/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51.c
index 76857bb161..dd4fc2bf4f 100644
--- a/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51.c
+++ b/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51.c
@@ -83,7 +83,8 @@ void SystemInit(void)
 
     // Start the external 32khz crystal oscillator.
 
-#if defined(TARGET_DELTA_DFCM_NNN40) || defined(TARGET_HRM1017) || defined(TARGET_NRF_LFCLK_RC)
+    /* for Nordic devices without an external LF crystal */
+#if defined(TARGET_NRF_LFCLK_RC)
     NRF_CLOCK->LFCLKSRC             = (CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos);
 #else
     NRF_CLOCK->LFCLKSRC             = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);