diff --git a/apps/openmw/mwgui/windowmanagerimp.cpp b/apps/openmw/mwgui/windowmanagerimp.cpp
index 6421df8241..40180d700e 100644
--- a/apps/openmw/mwgui/windowmanagerimp.cpp
+++ b/apps/openmw/mwgui/windowmanagerimp.cpp
@@ -1092,7 +1092,11 @@ namespace MWGui
             else if (it->first == "GUI" && it->second == "subtitles")
                 mSubtitlesEnabled = Settings::Manager::getBool ("subtitles", "GUI");
             else if (it->first == "GUI" && it->second == "menu transparency")
+            {
+                mViewer->stopThreading();
                 setMenuTransparency(Settings::Manager::getFloat("menu transparency", "GUI"));
+                mViewer->startThreading();
+            }
         }
     }
 
diff --git a/components/myguiplatform/myguitexture.hpp b/components/myguiplatform/myguitexture.hpp
index de385e94d6..109858bc8b 100644
--- a/components/myguiplatform/myguitexture.hpp
+++ b/components/myguiplatform/myguitexture.hpp
@@ -42,6 +42,8 @@ namespace osgMyGUI
 
         virtual void destroy();
 
+        /// @warning If you intend to change a texture during the frame update, you must either declare the texture with DataVariance::DYNAMIC
+        /// or temporarily stop the viewer threading, to prevent race conditions with the draw thread.
         virtual void* lock(MyGUI::TextureUsage access);
         virtual void unlock();
         virtual bool isLocked();