diff --git a/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51822.c b/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51822.c
index bae4156721..ae6d214f8f 100644
--- a/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51822.c
+++ b/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/system_nrf51822.c
@@ -66,7 +66,7 @@ void SystemInit(void)
 
     // Start the external 32khz crystal oscillator.
 
-#if defined(TARGET_HRM1017) | defined(TARGET_DELTA_DFCM_NNN40)
+#if defined(TARGET_HRM1017) || defined(TARGET_DELTA_DFCM_NNN40)
     NRF_CLOCK->LFCLKSRC             = (CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos);
 #else
     NRF_CLOCK->LFCLKSRC             = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);