diff --git a/cpu/samd21/cpu.c b/cpu/samd21/cpu.c
index 432043d5eb..da5291b25f 100644
--- a/cpu/samd21/cpu.c
+++ b/cpu/samd21/cpu.c
@@ -65,8 +65,7 @@ static void clk_init(void)
     SYSCTRL->DPLLCTRLB.reg = (SYSCTRL_DPLLCTRLB_REFCLK_GCLK);
     SYSCTRL->DPLLCTRLA.reg = (SYSCTRL_DPLLCTRLA_ENABLE);
     while(!(SYSCTRL->DPLLSTATUS.reg &
-           (SYSCTRL_DPLLSTATUS_CLKRDY | SYSCTRL_DPLLSTATUS_LOCK)) ==
-           (SYSCTRL_DPLLSTATUS_CLKRDY | SYSCTRL_DPLLSTATUS_LOCK));
+           (SYSCTRL_DPLLSTATUS_CLKRDY | SYSCTRL_DPLLSTATUS_LOCK)));
 
     /* select the PLL as source for clock generator 0 (CPU core clock) */
     GCLK->GENDIV.reg =  (GCLK_GENDIV_DIV(CLOCK_PLL_DIV) |