diff --git a/TESTS/host_tests/pyusb_basic.py b/TESTS/host_tests/pyusb_basic.py
index 54ecc265e4a..dc724ffaed4 100644
--- a/TESTS/host_tests/pyusb_basic.py
+++ b/TESTS/host_tests/pyusb_basic.py
@@ -1376,7 +1376,7 @@ def ep_test_abort(dev, log, verbose=False):
             payload_size = (NUM_PACKETS_UNTIL_ABORT + NUM_PACKETS_AFTER_ABORT) * ep_out.wMaxPacketSize
             num_bytes_written = 0
             while num_bytes_written < payload_size:
-                payload_out = array.array('B', (num_bytes_written/ep_out.wMaxPacketSize
+                payload_out = array.array('B', (num_bytes_written//ep_out.wMaxPacketSize
                                                 for _ in range(ep_out.wMaxPacketSize)))
                 try:
                     num_bytes_written += ep_out.write(payload_out)
diff --git a/TESTS/host_tests/usb_device_serial.py b/TESTS/host_tests/usb_device_serial.py
index e7c049cb218..c271176aa06 100644
--- a/TESTS/host_tests/usb_device_serial.py
+++ b/TESTS/host_tests/usb_device_serial.py
@@ -24,6 +24,7 @@
 import sys
 import serial
 import serial.tools.list_ports as stlp
+import six
 import mbed_host_tests
 
 
@@ -268,7 +269,7 @@ def change_line_coding(self):
         mbed_serial.reset_output_buffer()
         mbed_serial.dtr = True
         try:
-            payload = mbed_serial.read(LINE_CODING_STRLEN)
+            payload = six.ensure_str(mbed_serial.read(LINE_CODING_STRLEN))
             while len(payload) == LINE_CODING_STRLEN:
                 baud, bits, parity, stop = (int(i) for i in payload.split(','))
                 new_line_coding = {
@@ -277,7 +278,7 @@ def change_line_coding(self):
                     'parity': self._PARITIES[parity],
                     'stopbits': self._STOPBITS[stop]}
                 mbed_serial.apply_settings(new_line_coding)
-                payload = mbed_serial.read(LINE_CODING_STRLEN)
+                payload = six.ensure_str(mbed_serial.read(LINE_CODING_STRLEN))
         except serial.SerialException as exc:
             self.log('TEST ERROR: {}'.format(exc))
             self.notify_complete(False)
diff --git a/requirements.txt b/requirements.txt
index bcfb24342a6..c58992419e0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,7 +5,7 @@ junit-xml==1.8
 pyyaml==4.2b1
 jsonschema==2.6.0
 future==0.16.0
-six==1.11.0
+six==1.12.0
 mbed-cloud-sdk>=2.0.6,<2.1
 requests>=2.20,<2.21
 idna>=2,<2.8