diff --git a/MTMR/BrightnessViewController.swift b/MTMR/BrightnessViewController.swift
index fb6bc27..3206c0c 100644
--- a/MTMR/BrightnessViewController.swift
+++ b/MTMR/BrightnessViewController.swift
@@ -9,7 +9,11 @@ class BrightnessViewController: NSCustomTouchBarItem {
     init(identifier: NSTouchBarItem.Identifier, refreshInterval: Double, image: NSImage? = nil) {
         super.init(identifier: identifier)
         
-        sliderItem = CustomSlider(knob: image!)
+        if (image == nil) {
+            sliderItem = CustomSlider()
+        } else {
+            sliderItem = CustomSlider(knob: image!)
+        }
         sliderItem.target = self
         sliderItem.action =  #selector(BrightnessViewController.sliderValueChanged(_:))
         sliderItem.minValue = 0.0
diff --git a/MTMR/VolumeViewController.swift b/MTMR/VolumeViewController.swift
index 30ab919..9fa1960 100644
--- a/MTMR/VolumeViewController.swift
+++ b/MTMR/VolumeViewController.swift
@@ -18,7 +18,11 @@ class VolumeViewController: NSCustomTouchBarItem {
                          onAudioObjectID: defaultDeviceID,
                          forPropertyAddress: &forPropertyAddress)
         
-        sliderItem = CustomSlider(knob: image!)
+        if (image == nil) {
+            sliderItem = CustomSlider()
+        } else {
+            sliderItem = CustomSlider(knob: image!)
+        }
         sliderItem.target = self
         sliderItem.action =  #selector(VolumeViewController.sliderValueChanged(_:))        
         sliderItem.minValue = 0.0