diff --git a/ports/esp32/mpthreadport.c b/ports/esp32/mpthreadport.c
index 140a76464f..bbfc53d3f5 100644
--- a/ports/esp32/mpthreadport.c
+++ b/ports/esp32/mpthreadport.c
@@ -166,6 +166,8 @@ void mp_thread_finish(void) {
     mp_thread_mutex_unlock(&thread_mutex);
 }
 
+// This is called from the FreeRTOS idle task and is not within Python context,
+// so MP_STATE_THREAD is not valid and it does not have the GIL.
 void vPortCleanUpTCB(void *tcb) {
     if (thread == NULL) {
         // threading not yet initialised
@@ -182,8 +184,7 @@ void vPortCleanUpTCB(void *tcb) {
                 // move the start pointer
                 thread = th->next;
             }
-            // explicitly release all its memory
-            m_del(thread_t, th, 1);
+            // The "th" memory will eventually be reclaimed by the GC.
             break;
         }
     }