diff --git a/core/threaded/reactor_threaded.c b/core/threaded/reactor_threaded.c
index 392f49c31..14d84fd14 100644
--- a/core/threaded/reactor_threaded.c
+++ b/core/threaded/reactor_threaded.c
@@ -1112,6 +1112,7 @@ int lf_reactor_c_main(int argc, const char* argv[]) {
         // run on the main thread, rather than creating a new thread.
         // This is important for bare-metal platforms, who can't
         // afford to have the main thread sit idle.
+        env->thread_ids[j] = lf_thread_self();
         continue;
       }
       if (lf_thread_create(&env->thread_ids[j], worker, env) != 0) {
diff --git a/low_level_platform/impl/src/lf_arduino_support.c b/low_level_platform/impl/src/lf_arduino_support.c
index ed9391205..5793bd650 100644
--- a/low_level_platform/impl/src/lf_arduino_support.c
+++ b/low_level_platform/impl/src/lf_arduino_support.c
@@ -170,6 +170,13 @@ typedef void* (*lf_function_t)(void*);
  */
 int lf_available_cores() { return 1; }
 
+lf_thread_t lf_thread_self() {
+  // Not implemented. Although Arduino mbed provides a ThisThread API and a
+  // get_id() function, it does not provide a way to get the current thread as a
+  // Thread object.
+  return NULL;
+}
+
 int lf_thread_create(lf_thread_t* thread, void* (*lf_thread)(void*), void* arguments) {
   lf_thread_t t = thread_new();
   long int start = thread_start(t, *lf_thread, arguments);
diff --git a/low_level_platform/impl/src/lf_flexpret_support.c b/low_level_platform/impl/src/lf_flexpret_support.c
index 9d83283c5..cf37c1b8a 100644
--- a/low_level_platform/impl/src/lf_flexpret_support.c
+++ b/low_level_platform/impl/src/lf_flexpret_support.c
@@ -178,6 +178,11 @@ int lf_available_cores() {
   return FP_THREADS - 1; // Return the number of Flexpret HW threads
 }
 
+lf_thread_t lf_thread_self() {
+  // Not implemented.
+  return NULL;
+}
+
 int lf_thread_create(lf_thread_t* thread, void* (*lf_thread)(void*), void* arguments) {
   /**
    * Need to select between HRTT or SRTT; see
diff --git a/low_level_platform/impl/src/lf_windows_support.c b/low_level_platform/impl/src/lf_windows_support.c
index 1d48bc6c7..61424ac7f 100644
--- a/low_level_platform/impl/src/lf_windows_support.c
+++ b/low_level_platform/impl/src/lf_windows_support.c
@@ -162,6 +162,8 @@ int lf_available_cores() {
   return sysinfo.dwNumberOfProcessors;
 }
 
+lf_thread_t lf_thread_self() { return GetCurrentThread(); }
+
 int lf_thread_create(lf_thread_t* thread, void* (*lf_thread)(void*), void* arguments) {
   uintptr_t handle = _beginthreadex(NULL, 0, lf_thread, arguments, 0, NULL);
   *thread = (HANDLE)handle;