diff --git a/extmod/modtrezorui/display-stmhal.h b/extmod/modtrezorui/display-stmhal.h
index 32c77a41..7b288eed 100644
--- a/extmod/modtrezorui/display-stmhal.h
+++ b/extmod/modtrezorui/display-stmhal.h
@@ -203,9 +203,9 @@ void display_update(void) {
 
 int display_backlight(int val)
 {
-    if (val >= 0 && val <= 255) {
+    if (BACKLIGHT != val && val >= 0 && val <= 255) {
         BACKLIGHT = val;
+        __HAL_TIM_SetCompare(&TIM1_Handle, TIM_CHANNEL_1, LED_PWM_TIM_PERIOD * BACKLIGHT / 255);
     }
-    __HAL_TIM_SetCompare(&TIM1_Handle, TIM_CHANNEL_1, LED_PWM_TIM_PERIOD * BACKLIGHT / 255);
     return BACKLIGHT;
 }
diff --git a/extmod/modtrezorui/display-unix.h b/extmod/modtrezorui/display-unix.h
index 46f3bdab..1b5dcc42 100644
--- a/extmod/modtrezorui/display-unix.h
+++ b/extmod/modtrezorui/display-unix.h
@@ -128,9 +128,9 @@ int display_orientation(int degrees)
 
 int display_backlight(int val)
 {
-    if (val >= 0 && val <= 255) {
+    if (BACKLIGHT != val && val >= 0 && val <= 255) {
         BACKLIGHT = val;
+        SDL_SetRenderDrawColor(RENDERER, BACKLIGHT, BACKLIGHT, BACKLIGHT, 255);
     }
-    SDL_SetRenderDrawColor(RENDERER, BACKLIGHT, BACKLIGHT, BACKLIGHT, 255);
     return BACKLIGHT;
 }