diff --git a/cpu/stm32f1/cpu.c b/cpu/stm32f1/cpu.c
index e30ef52e07..89d69198ed 100644
--- a/cpu/stm32f1/cpu.c
+++ b/cpu/stm32f1/cpu.c
@@ -111,7 +111,6 @@ static void clk_init(void)
     /* PCLK1 = HCLK */
     RCC->CFGR |= (uint32_t)CLOCK_APB1_DIV;
     /*  PLL configuration: PLLCLK = CLOCK_SOURCE / PLL_DIV * PLL_MUL */
-    RCC->CFGR &= ~((uint32_t)(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLMULL));
     RCC->CFGR |= (uint32_t)(CLOCK_PLL_SOURCE | CLOCK_PLL_DIVMSK | ((CLOCK_PLL_MUL - 2) << 18));
     /* Enable PLL */
     RCC->CR |= RCC_CR_PLLON;