diff --git a/tools/mpremote/src/mpremote/pyboardextended.py b/tools/mpremote/src/mpremote/pyboardextended.py
index 4b676bc30da73..ed556633a5b03 100644
--- a/tools/mpremote/src/mpremote/pyboardextended.py
+++ b/tools/mpremote/src/mpremote/pyboardextended.py
@@ -71,11 +71,15 @@ def rd_into(self, buf, n):
     def begin(self, type):
         micropython.kbd_intr(-1)
         buf4 = self.buf4
-        while self.poller.poll(0):
-            self.fin.readinto(buf4, 1)
         buf4[0] = 0x18
         buf4[1] = type
         self.fout.write(buf4, 2)
+        # Wait for sync byte 0x18, but don't get stuck forever
+        for i in range(30):
+            self.poller.poll(1000)
+            self.fin.readinto(buf4, 1)
+            if buf4[0] == 0x18:
+                break
 
     def end(self):
         micropython.kbd_intr(3)
@@ -502,6 +506,7 @@ def _check_input(self, blocking):
             if c == b"\x18":
                 # a special command
                 c = self.orig_serial.read(1)[0]
+                self.orig_serial.write(b"\x18")  # Acknowledge command
                 PyboardCommand.cmd_table[c](self.cmd)
             elif not VT_ENABLED and c == b"\x1b":
                 # ESC code, ignore these on windows