diff --git a/os/hal/ports/STM32/LLD/TIMv1/hal_pwm_lld.c b/os/hal/ports/STM32/LLD/TIMv1/hal_pwm_lld.c
index a59105215..6bf31ebc0 100644
--- a/os/hal/ports/STM32/LLD/TIMv1/hal_pwm_lld.c
+++ b/os/hal/ports/STM32/LLD/TIMv1/hal_pwm_lld.c
@@ -771,8 +771,8 @@ void pwm_lld_enable_periodic_notification(PWMDriver *pwmp) {
   /* If the IRQ is not already enabled care must be taken to clear it,
      it is probably already pending because the timer is running.*/
   if ((dier & STM32_TIM_DIER_UIE) == 0) {
+    pwmp->tim->SR   = ~STM32_TIM_SR_UIF;
     pwmp->tim->DIER = dier | STM32_TIM_DIER_UIE;
-    pwmp->tim->SR &= STM32_TIM_SR_UIF;
   }
 }
 
@@ -813,8 +813,8 @@ void pwm_lld_enable_channel_notification(PWMDriver *pwmp,
   /* If the IRQ is not already enabled care must be taken to clear it,
      it is probably already pending because the timer is running.*/
   if ((dier & (2 << channel)) == 0) {
-    pwmp->tim->DIER = dier | (2 << channel);
     pwmp->tim->SR   = ~(2 << channel);
+    pwmp->tim->DIER = dier | (2 << channel);
   }
 }
 
diff --git a/readme.txt b/readme.txt
index 84a5c8b5e..dbb79d4f3 100644
--- a/readme.txt
+++ b/readme.txt
@@ -111,6 +111,8 @@
 - EX:  Updated LIS302DL to 1.1.0 (backported to 18.2.1).
 - EX:  Updated LPS25H to 1.1.0 (backported to 18.2.1).
 - EX:  Updated LSM303DLHC to 1.1.0 (backported to 18.2.1).
+- HAL: Fixed problem clearing UIF timer flag in STM32 PWM driver (bug #934)
+       (backported to 18.2.1 and 17.6.5).
 - HAL: Fixed USB Serial driver problem with zero-size OUT transactions
        (bug #933)(backported to 18.2.1 and 17.6.5).
 - HAL: Fixed race condition in STM32 QSPI driver (bug #932)(backported to