Index: source/tools/atlas/AtlasUI/ScenarioEditor/ScenarioEditor.cpp
===================================================================
--- source/tools/atlas/AtlasUI/ScenarioEditor/ScenarioEditor.cpp
+++ source/tools/atlas/AtlasUI/ScenarioEditor/ScenarioEditor.cpp
@@ -576,7 +576,6 @@
 
 	// Send setup messages to game engine:
 
-	POST_MESSAGE(InitSDL, ());
 
 	POST_MESSAGE(SetCanvas, (static_cast<wxGLCanvas*>(canvas),
 		canvas->GetClientSize().GetWidth(), canvas->GetClientSize().GetHeight()));
Index: source/tools/atlas/GameInterface/GameLoop.cpp
===================================================================
--- source/tools/atlas/GameInterface/GameLoop.cpp
+++ source/tools/atlas/GameInterface/GameLoop.cpp
@@ -308,6 +308,10 @@
 	// Tell Atlas the location of the user config directory
 	Atlas_SetConfigDirectory(paths.Config().string().c_str());
 
+	// SDL must be call in the main thread on osx
+	SDL_InitSubSystem(SDL_INIT_VIDEO);
+	SDL_GL_LoadLibrary(nullptr); // NULL = use default
+
 	// Run the engine loop in a new thread
 	pthread_t engineThread;
 	pthread_create(&engineThread, NULL, RunEngine, reinterpret_cast<void*>(const_cast<CmdLineArgs*>(&args)));
Index: source/tools/atlas/GameInterface/Handlers/GraphicsSetupHandlers.cpp
===================================================================
--- source/tools/atlas/GameInterface/Handlers/GraphicsSetupHandlers.cpp
+++ source/tools/atlas/GameInterface/Handlers/GraphicsSetupHandlers.cpp
@@ -62,25 +62,6 @@
 	g_VideoMode.InitNonSDL();
 }
 
-MESSAGEHANDLER(InitSDL)
-{
-	UNUSED2(msg);
-
-	// When using GLX (Linux), SDL has to load the GL library to find
-	// glXGetProcAddressARB before it can load any extensions.
-	// When running in Atlas, we skip the SDL video initialisation code
-	// which loads the library, and so SDL_GL_GetProcAddress fails (in
-	// ogl.cpp importExtensionFunctions).
-	// (TODO: I think this is meant to be context-independent, i.e. it
-	// doesn't matter that we're getting extensions from SDL-initialised
-	// GL stuff instead of from the wxWidgets-initialised GL stuff, but that
-	// should be checked.)
-	// So, make sure it's loaded:
-	SDL_InitSubSystem(SDL_INIT_VIDEO);
-	SDL_GL_LoadLibrary(NULL); // NULL = use default
-	// (it shouldn't hurt if this is called multiple times, I think)
-}
-
 MESSAGEHANDLER(InitGraphics)
 {
 	UNUSED2(msg);
Index: source/tools/atlas/GameInterface/Messages.h
===================================================================
--- source/tools/atlas/GameInterface/Messages.h
+++ source/tools/atlas/GameInterface/Messages.h
@@ -37,9 +37,6 @@
 // Initialise some engine code. Must be called before anything else.
 MESSAGE(Init, );
 
-// Initialise SDL-related code. Must be called before SetCanvas and InitGraphics.
-MESSAGE(InitSDL, );
-
 // Initialise graphics-related code. Must be called after the first SetCanvas,
 // and before much else.
 MESSAGE(InitGraphics, );