diff --git a/cpu/stm32_common/periph/rtc.c b/cpu/stm32_common/periph/rtc.c
index fa513f12d2..78c8fe546e 100644
--- a/cpu/stm32_common/periph/rtc.c
+++ b/cpu/stm32_common/periph/rtc.c
@@ -237,7 +237,7 @@ void rtc_init(void)
     EXTI->FTSR &= ~(EXTI_FTSR_BIT);
     EXTI->RTSR |= EXTI_RTSR_BIT;
     EXTI->IMR  |= EXTI_IMR_BIT;
-    EXTI->PR   |= EXTI_PR_BIT;
+    EXTI->PR   = EXTI_PR_BIT;
     /* enable global RTC interrupt */
     NVIC_EnableIRQ(IRQN);
 }
@@ -351,7 +351,7 @@ void ISR_NAME(void)
         }
         RTC->ISR &= ~RTC_ISR_ALRAF;
     }
-    EXTI->PR |= EXTI_PR_BIT;
+    EXTI->PR = EXTI_PR_BIT; /* only clear the associated bit */
     cortexm_isr_end();
 }
 
diff --git a/cpu/stm32_common/periph/rtt.c b/cpu/stm32_common/periph/rtt.c
index 5b59f32903..5ede032e2b 100644
--- a/cpu/stm32_common/periph/rtt.c
+++ b/cpu/stm32_common/periph/rtt.c
@@ -115,7 +115,7 @@ void rtt_init(void)
     !defined(CPU_FAM_STM32WB)
     EXTI->FTSR_REG &= ~(EXTI_FTSR_BIT);
     EXTI->RTSR_REG |= EXTI_RTSR_BIT;
-    EXTI->PR_REG |= EXTI_PR_BIT;
+    EXTI->PR_REG = EXTI_PR_BIT;
 #endif
     NVIC_EnableIRQ(LPTIM1_IRQn);
     /* enable timer */
@@ -206,7 +206,7 @@ void isr_lptim1(void)
     LPTIM1->ICR = (LPTIM_ICR_ARRMCF | LPTIM_ICR_CMPMCF);
 #if !defined(CPU_FAM_STM32L4) && !defined(CPU_FAM_STM32L0) && \
     !defined(CPU_FAM_STM32WB)
-    EXTI->PR_REG |= EXTI_PR_BIT;
+    EXTI->PR_REG = EXTI_PR_BIT; /* only clear the associated bit */
 #endif
 
     cortexm_isr_end();