diff --git a/include/libremidi/api.hpp b/include/libremidi/api.hpp
index 2a957fcf..ce5ba692 100644
--- a/include/libremidi/api.hpp
+++ b/include/libremidi/api.hpp
@@ -62,8 +62,8 @@ inline constexpr libremidi::API default_api() noexcept
   return API::WINDOWS_MM;
 #elif defined(LIBREMIDI_ALSA)
   return API::ALSA_SEQ;
-#elif defined(__emscripten__)
-  return API::EMSCRIPTEN_WEBMIDI;
+#elif defined(__EMSCRIPTEN__)
+  return API::WEBMIDI;
 #elif defined(LIBREMIDI_ANDROID)
   return API::ANDROID_AMIDI;
 #else
@@ -83,7 +83,7 @@ inline constexpr libremidi::API default_api() noexcept
   return API::WINDOWS_MIDI_SERVICES;
 #elif defined(LIBREMIDI_ALSA)
   return API::ALSA_SEQ_UMP;
-#elif defined(__emscripten__)
+#elif defined(__EMSCRIPTEN__)
   return API::DUMMY;
 #else
   return API::DUMMY;
diff --git a/include/libremidi/backends/emscripten/midi_access.hpp b/include/libremidi/backends/emscripten/midi_access.hpp
index 02708a7b..8f3a9957 100644
--- a/include/libremidi/backends/emscripten/midi_access.hpp
+++ b/include/libremidi/backends/emscripten/midi_access.hpp
@@ -303,10 +303,10 @@ class midi_access_emscripten
       return;
 
     const auto& id = m_current_inputs[port_index].id;
-    EM_ASM(const id = UTF8ToString($1);
+    EM_ASM(const id = UTF8ToString($0);
 
            let input = globalThis.__libreMidi_access.inputs.get(id);
-           input.onmidimessage = undefined;, id.c_str());
+           if (input) input.onmidimessage = null;, id.c_str());
   }
 
   std::vector<observer_emscripten*> m_observers;
diff --git a/include/libremidi/backends/emscripten/observer.cpp b/include/libremidi/backends/emscripten/observer.cpp
index 6c895156..9e5e0cb5 100644
--- a/include/libremidi/backends/emscripten/observer.cpp
+++ b/include/libremidi/backends/emscripten/observer.cpp
@@ -92,14 +92,14 @@ LIBREMIDI_INLINE void observer_emscripten::update(
   for (std::size_t i = m_known_inputs.size(); i < current_inputs.size(); i++)
   {
     m_known_inputs.push_back(current_inputs[i]);
-    if (notify)
+    if (notify && configuration.input_added)
       configuration.input_added(to_port_info<true>(i, m_known_inputs[i]));
   }
 
   for (std::size_t i = m_known_outputs.size(); i < current_outputs.size(); i++)
   {
     m_known_outputs.push_back(current_outputs[i]);
-    if (notify)
+    if (notify && configuration.output_added)
       configuration.output_added(to_port_info<false>(i, m_known_outputs[i]));
   }
 }