diff --git a/firmware/backlight.c b/firmware/backlight.c
index 507f252e6d..3b58637362 100644
--- a/firmware/backlight.c
+++ b/firmware/backlight.c
@@ -83,8 +83,9 @@ void backlight_start_timer(void)
         return ;
         
     /* Prevent cpu frequency changes while dimming. */
+#ifdef HAVE_ADJUSTABLE_CPU_FREQ
     cpu_boost(true);
-    
+#endif    
     count = 1;
     bl_timer_active = true;
 
@@ -155,7 +156,9 @@ void TIMER1(void)
 
     if (idle) 
     {
-        cpu_boost(false);
+#ifdef HAVE_ADJUSTABLE_CPU_FREQ
+        cpu_boost(true);
+#endif    
         bl_timer_active = false;
         TMR1 = 0;
     }
@@ -177,7 +180,9 @@ void backlight_allow_timer(bool on)
 
     if (!timer_allowed && bl_timer_active)
     {
-        cpu_boost(false);
+#ifdef HAVE_ADJUSTABLE_CPU_FREQ
+        cpu_boost(true);
+#endif    
         bl_dim_current = bl_dim_target;
         bl_timer_active = false;
         TMR1 = 0;
diff --git a/firmware/pcm_playback.c b/firmware/pcm_playback.c
index 75dc792389..5c25649d76 100644
--- a/firmware/pcm_playback.c
+++ b/firmware/pcm_playback.c
@@ -114,7 +114,9 @@ void pcm_boost(bool state)
         return ;
         
     if (state != boost_state) {
+#ifdef HAVE_ADJUSTABLE_CPU_FREQ
         cpu_boost(state);
+#endif    
         boost_state = state;
     }
 }