diff --git a/apps/openmw/mwrender/renderingmanager.cpp b/apps/openmw/mwrender/renderingmanager.cpp
index 9258b754f7..5449fd4608 100644
--- a/apps/openmw/mwrender/renderingmanager.cpp
+++ b/apps/openmw/mwrender/renderingmanager.cpp
@@ -244,7 +244,7 @@ namespace MWRender
         for (auto itr = shadowDefines.begin(); itr != shadowDefines.end(); itr++)
             globalDefines[itr->first] = itr->second;
 
-        mResourceSystem->getSceneManager()->getShaderManager().setGlobalDefines(globalDefines);
+        mResourceSystem->getSceneManager()->getShaderManager().setGlobalDefines(globalDefines, mViewer);
 
         mPathgrid.reset(new Pathgrid(mRootNode));
 
diff --git a/components/shader/shadermanager.cpp b/components/shader/shadermanager.cpp
index 3b18d0b756..533b3ae561 100644
--- a/components/shader/shadermanager.cpp
+++ b/components/shader/shadermanager.cpp
@@ -337,10 +337,29 @@ namespace Shader
         return DefineMap(mGlobalDefines);
     }
 
-    void ShaderManager::setGlobalDefines(DefineMap & defines)
+    void ShaderManager::setGlobalDefines(DefineMap & defines, osg::ref_ptr<osgViewer::Viewer> viewer)
     {
         mGlobalDefines = defines;
-        // TODO: We need to trigger the regeneration of all shaders.
+        bool threadsStarted = viewer->areThreadsRunning();
+        if (threadsStarted)
+            viewer->stopThreading();
+        for (auto shaderMapElement: mShaders)
+        {
+            std::string templateId = shaderMapElement.first.first;
+            ShaderManager::DefineMap defines = shaderMapElement.first.second;
+            osg::ref_ptr<osg::Shader> shader = shaderMapElement.second;
+            if (shader == nullptr)
+                // I'm not sure how to handle a shader that was already broken as there's no way to get a potential replacement to the nodes that need it.
+                continue;
+            std::string shaderSource = mShaderTemplates[templateId];
+            if (!parseDefines(shaderSource, defines, mGlobalDefines) || !parseFors(shaderSource))
+                // We just broke the shader and there's no way to force existing objects back to fixed-function mode as we would when creating the shader.
+                // If we put a nullptr in the shader map, we just lose the ability to put a working one in later.
+                continue;
+            shader->setShaderSource(shaderSource);
+        }
+        if (threadsStarted)
+            viewer->startThreading();
     }
 
     void ShaderManager::releaseGLObjects(osg::State *state)
diff --git a/components/shader/shadermanager.hpp b/components/shader/shadermanager.hpp
index baaa738659..16b4d639bb 100644
--- a/components/shader/shadermanager.hpp
+++ b/components/shader/shadermanager.hpp
@@ -8,6 +8,8 @@
 
 #include <osg/Shader>
 
+#include <osgViewer/Viewer>
+
 #include <OpenThreads/Mutex>
 
 namespace Shader
@@ -37,7 +39,7 @@ namespace Shader
 
         /// Set the DefineMap used to construct all shaders
         /// @param defines The DefineMap to use
-        void setGlobalDefines(DefineMap& defines);
+        void setGlobalDefines(DefineMap & defines, osg::ref_ptr<osgViewer::Viewer> viewer);
 
         void releaseGLObjects(osg::State* state);