diff --git a/drivers/Serial.h b/drivers/Serial.h
index 434d6aa177..1b1e6aa34e 100644
--- a/drivers/Serial.h
+++ b/drivers/Serial.h
@@ -82,6 +82,10 @@ public:
      */
     Serial(PinName tx, PinName rx, int baud);
 
+    /* Stream gives us a FileHandle with non-functional poll()/readable()/writable. Pass through
+     * the calls from the SerialBase instead for backwards compatibility. This problem is
+     * part of why Stream and Serial should be deprecated.
+     */
     bool readable()
     {
         return SerialBase::readable();