diff --git a/docs/reference/mpremote.rst b/docs/reference/mpremote.rst
index bb0686237a..3225fc5f24 100644
--- a/docs/reference/mpremote.rst
+++ b/docs/reference/mpremote.rst
@@ -19,10 +19,10 @@ The simplest way to use this tool is just by invoking it without any arguments:
 
     mpremote
 
-This command automatically detects and connects to the first available serial
-device and provides an interactive REPL.  Serial ports are opened in exclusive
-mode, so running a second (or third, etc) instance of ``mpremote`` will connect
-to subsequent serial devices, if any are available.
+This command automatically detects and connects to the first available USB
+serial device and provides an interactive REPL.  Serial ports are opened in
+exclusive mode, so running a second (or third, etc) instance of ``mpremote``
+will connect to subsequent serial devices, if any are available.
 
 
 Commands
@@ -52,7 +52,7 @@ The full list of supported commands are:
   ``<device>`` may be one of:
 
   - ``list``: list available devices
-  - ``auto``: connect to the first available device
+  - ``auto``: connect to the first available USB serial port
   - ``id:<serial>``: connect to the device with USB serial number
     ``<serial>`` (the second entry in the output from the ``connect list``
     command)
@@ -186,8 +186,8 @@ Auto connection and soft-reset
 
 Connection and disconnection will be done automatically at the start and end of
 the execution of the tool, if such commands are not explicitly given.  Automatic
-connection will search for the first available serial device. If no action is
-specified then the REPL will be entered.
+connection will search for the first available USB serial device. If no action
+is specified then the REPL will be entered.
 
 Once connected to a device, ``mpremote`` will automatically soft-reset the
 device if needed.  This clears the Python heap and restarts the interpreter,
diff --git a/tools/mpremote/README.md b/tools/mpremote/README.md
index 7f58788fbe..4eb1b86fb4 100644
--- a/tools/mpremote/README.md
+++ b/tools/mpremote/README.md
@@ -7,7 +7,7 @@ The simplest way to use this tool is:
 
     mpremote
 
-This will automatically connect to the device and provide an interactive REPL.
+This will automatically connect to a USB serial port and provide an interactive REPL.
 
 The full list of supported commands are:
 
diff --git a/tools/mpremote/mpremote/commands.py b/tools/mpremote/mpremote/commands.py
index 3bd8732bd0..d05a27d9f2 100644
--- a/tools/mpremote/mpremote/commands.py
+++ b/tools/mpremote/mpremote/commands.py
@@ -32,14 +32,15 @@ def do_connect(state, args=None):
             # Don't do implicit REPL command.
             state.did_action()
         elif dev == "auto":
-            # Auto-detect and auto-connect to the first available device.
+            # Auto-detect and auto-connect to the first available USB serial port.
             for p in sorted(serial.tools.list_ports.comports()):
-                try:
-                    state.pyb = pyboard.PyboardExtended(p.device, baudrate=115200)
-                    return
-                except pyboard.PyboardError as er:
-                    if not er.args[0].startswith("failed to access"):
-                        raise er
+                if p.vid is not None and p.pid is not None:
+                    try:
+                        state.pyb = pyboard.PyboardExtended(p.device, baudrate=115200)
+                        return
+                    except pyboard.PyboardError as er:
+                        if not er.args[0].startswith("failed to access"):
+                            raise er
             raise pyboard.PyboardError("no device found")
         elif dev.startswith("id:"):
             # Search for a device with the given serial number.