diff --git a/radiant/ui/lightinspector/LightInspector.cpp b/radiant/ui/lightinspector/LightInspector.cpp
index c2ba916b75..0c6094b6a6 100644
--- a/radiant/ui/lightinspector/LightInspector.cpp
+++ b/radiant/ui/lightinspector/LightInspector.cpp
@@ -150,11 +150,26 @@ void LightInspector::setupOptionsPanel()
     findNamedObject<wxColourPickerCtrl>(this, "LightInspectorColour")->Bind(
         wxEVT_COLOURPICKER_CHANGED, &LightInspector::_onColourChange, this
     );
-    _brightnessSlider->Bind(
-        wxEVT_SLIDER, [=](wxCommandEvent&) { adjustBrightness(); }
+    _brightnessSlider->Bind( // drag in progress
+        wxEVT_SCROLL_THUMBTRACK,
+        [=](wxScrollEvent&) {
+            if (!_adjustingBrightness && !GlobalUndoSystem().operationStarted())
+            {
+                GlobalUndoSystem().start();
+                _adjustingBrightness = true;
+            }
+            adjustBrightness();
+        }
     );
-    _brightnessSlider->Bind(
-        wxEVT_SCROLL_CHANGED, [=](wxScrollEvent&) { updateColourPicker(); }
+    _brightnessSlider->Bind( // drag finished
+        wxEVT_SCROLL_CHANGED,
+        [=](wxScrollEvent&) {
+            if (_adjustingBrightness) {
+                GlobalUndoSystem().finish("Adjust light brightness");
+                _adjustingBrightness = false;
+            }
+            updateColourPicker();
+        }
     );
 
     findNamedObject<wxCheckBox>(this, "LightInspectorParallel")->Bind(wxEVT_CHECKBOX, &LightInspector::_onOptionsToggle, this);
diff --git a/radiant/ui/lightinspector/LightInspector.h b/radiant/ui/lightinspector/LightInspector.h
index 5c096db4e5..a4035fccd6 100644
--- a/radiant/ui/lightinspector/LightInspector.h
+++ b/radiant/ui/lightinspector/LightInspector.h
@@ -48,6 +48,10 @@ class LightInspector :
     // Disables callbacks if set to TRUE (during widget updates)
     bool _updateActive;
 
+    // Track if a brightness adjustment is in progress (which needs an undo
+    // command when finished)
+    bool _adjustingBrightness = false;
+
     bool _supportsAiSee;
 
     sigc::connection _selectionChanged;