diff --git a/dist/pythonlibs/testrunner/spawn.py b/dist/pythonlibs/testrunner/spawn.py
index 606114175..032618a24 100644
--- a/dist/pythonlibs/testrunner/spawn.py
+++ b/dist/pythonlibs/testrunner/spawn.py
@@ -28,6 +28,10 @@ MAKE_TERM_STARTED_DELAY = int(os.environ.get('TESTRUNNER_START_DELAY') or 3)
 # default value (0, no delay)
 MAKE_RESET_DELAY = int(os.environ.get('TESTRUNNER_RESET_DELAY') or 0)
 
+# Setting an empty 'TESTRUNNER_CONNECT_DELAY' environment variable use the
+# default value (0)
+MAKE_TERM_CONNECT_DELAY = int(os.environ.get('TESTRUNNER_CONNECT_DELAY') or 0)
+
 # Allow customizing test interactive settings with environment variables
 TEST_INTERACTIVE_RETRIES = int(os.environ.get('TEST_INTERACTIVE_RETRIES') or 5)
 TEST_INTERACTIVE_DELAY = int(os.environ.get('TEST_INTERACTIVE_DELAY') or 1)
@@ -66,6 +70,10 @@ def setup_child(timeout=10, spawnclass=pexpect.spawnu, env=None, logfile=None):
     # before `cleanterm`.
     _reset_board(env)
 
+    # on platforms exposing UART over USB, wait a little before connecting to
+    # the serial terminal. This gives time for stdio to be ready.
+    time.sleep(MAKE_TERM_CONNECT_DELAY)
+
     child = spawnclass("make cleanterm", env=env, timeout=timeout,
                        codec_errors='replace', echo=False)