diff --git a/scripts/src/main.lua b/scripts/src/main.lua
index a4bb6d3eab6..74bac36258c 100644
--- a/scripts/src/main.lua
+++ b/scripts/src/main.lua
@@ -153,6 +153,7 @@ end
 				.. " -s DISABLE_EXCEPTION_CATCHING=2"
 				.. " -s EXCEPTION_CATCHING_WHITELIST='[\"__ZN15running_machine17start_all_devicesEv\",\"__ZN12cli_frontend7executeEiPPc\"]'"
 				.. " -s EXPORTED_FUNCTIONS=\"['_main', '_malloc', '__ZN15running_machine30emscripten_get_running_machineEv', '__ZN15running_machine17emscripten_get_uiEv', '__ZN15running_machine20emscripten_get_soundEv', '__ZN15mame_ui_manager12set_show_fpsEb', '__ZNK15mame_ui_manager8show_fpsEv', '__ZN13sound_manager4muteEbh', '_SDL_PauseAudio', '_SDL_SendKeyboardKey', '__ZN15running_machine15emscripten_saveEPKc', '__ZN15running_machine15emscripten_loadEPKc', '__ZN15running_machine21emscripten_hard_resetEv', '__ZN15running_machine21emscripten_soft_resetEv', '__ZN15running_machine15emscripten_exitEv']\""
+				.. " -s EXTRA_EXPORTED_RUNTIME_METHODS=\"['cwrap']\""
 				.. " --pre-js " .. _MAKE.esc(MAME_DIR) .. "src/osd/modules/sound/js_sound.js"
 				.. " --post-js " .. _MAKE.esc(MAME_DIR) .. "scripts/resources/emscripten/emscripten_post.js"
 				.. " --embed-file " .. _MAKE.esc(MAME_DIR) .. "bgfx/chains@bgfx/chains"
diff --git a/src/osd/osdsync.cpp b/src/osd/osdsync.cpp
index 12253f2acbd..984d3b3b802 100644
--- a/src/osd/osdsync.cpp
+++ b/src/osd/osdsync.cpp
@@ -87,8 +87,13 @@ static void spin_while_not(const volatile _AtomType * volatile atom, const _Main
 
 int osd_get_num_processors(void)
 {
+#if defined(SDLMAME_EMSCRIPTEN)
+	// multithreading is not supported at this time
+	return 1;
+#else
 	// max out at 4 for now since scaling above that seems to do poorly
 	return std::min(std::thread::hardware_concurrency(), 4U);
+#endif
 }
 
 //============================================================