diff --git a/src/mono/mono/utils/mono-filemap.c b/src/mono/mono/utils/mono-filemap.c
index 4d7cd5f96b896a..0c4ac46a5b4970 100644
--- a/src/mono/mono/utils/mono-filemap.c
+++ b/src/mono/mono/utils/mono-filemap.c
@@ -40,11 +40,6 @@ mono_file_map_open (const char* name)
 	int fd = open (name, O_RDONLY);
 	if (fd < 0)
 		return NULL;
-#ifdef HOST_NUTTX
-	/* Track fd→path mapping for SDRAM cache in mmap stub */
-	extern void sdram_cache_track_fd(int fd, const char *path);
-	sdram_cache_track_fd (fd, name);
-#endif
 	return (MonoFileMap *)(size_t)fd;
 #endif
 }
diff --git a/src/native/libs/System.Native/pal_io.c b/src/native/libs/System.Native/pal_io.c
index 7c1d8af3b417c4..1af3c4b080d256 100644
--- a/src/native/libs/System.Native/pal_io.c
+++ b/src/native/libs/System.Native/pal_io.c
@@ -14,6 +14,7 @@
 #include <errno.h>
 #ifdef __NuttX__
 #include "pal_io_nuttx.h"
+#include "pal_networking.h"   // nxsock_close_notify
 #else
 #include <fnmatch.h>
 #endif
@@ -394,6 +395,10 @@ int32_t SystemNative_Close(intptr_t fd)
     // do it here. Harmless for non-socket fds (ENOTSOCK) and already-shutdown
     // sockets (ENOTCONN).
     shutdown(rawFd, SHUT_RDWR);
+
+    // Remove the fd from the SocketAsyncEngine poll() emulation before it is
+    // closed (see nxsock_close_notify in pal_networking.c).  Safe for any fd.
+    nxsock_close_notify(rawFd);
 #endif
 
     int result = close(rawFd);
diff --git a/src/native/minipal/thread.h b/src/native/minipal/thread.h
index b626f9ddea6bf3..0c10ff84c298be 100644
--- a/src/native/minipal/thread.h
+++ b/src/native/minipal/thread.h
@@ -88,6 +88,11 @@ static inline size_t minipal_get_current_thread_id(void)
 #if defined(__wasm) && !defined(_REENTRANT)
     return minipal_get_current_thread_id_no_cache();
 
+#elif defined(__NuttX__)
+    // NuttX user space has no thread-local storage support (__aeabi_read_tp is
+    // only provided in the kernel), so do not cache the ID.
+    return minipal_get_current_thread_id_no_cache();
+
 #else // !__wasm || _REENTRANT
 #if defined(__GNUC__) && !defined(__clang__) && defined(__cplusplus)
     // gcc doesn't like _Thread_local when __cplusplus is defined.