diff --git a/test/py/conftest.py b/test/py/conftest.py
index 3e162cafcc..09638e64a3 100644
--- a/test/py/conftest.py
+++ b/test/py/conftest.py
@@ -71,6 +71,9 @@ def pytest_addoption(parser):
         help='U-Boot board identity/instance')
     parser.addoption('--build', default=False, action='store_true',
         help='Compile U-Boot before running tests')
+    parser.addoption('--gdbserver', default=None,
+        help='Run sandbox under gdbserver. The argument is the channel '+
+        'over which gdbserver should communicate, e.g. localhost:1234')
 
 def pytest_configure(config):
     """pytest hook: Perform custom initialization at startup time.
@@ -110,6 +113,10 @@ def pytest_configure(config):
         persistent_data_dir = build_dir + '/persistent-data'
     mkdir_p(persistent_data_dir)
 
+    gdbserver = config.getoption('gdbserver')
+    if gdbserver and board_type != 'sandbox':
+        raise Exception('--gdbserver only supported with sandbox')
+
     import multiplexed_log
     log = multiplexed_log.Logfile(result_dir + '/test-log.html')
 
@@ -169,6 +176,7 @@ def pytest_configure(config):
     ubconfig.persistent_data_dir = persistent_data_dir
     ubconfig.board_type = board_type
     ubconfig.board_identity = board_identity
+    ubconfig.gdbserver = gdbserver
 
     env_vars = (
         'board_type',
diff --git a/test/py/tests/test_sleep.py b/test/py/tests/test_sleep.py
index 74add891c3..5c1a2623fe 100644
--- a/test/py/tests/test_sleep.py
+++ b/test/py/tests/test_sleep.py
@@ -15,6 +15,7 @@ def test_sleep(u_boot_console):
     u_boot_console.run_command('sleep %d' % sleep_time)
     tend = time.time()
     elapsed = tend - tstart
-    delta_to_expected = abs(elapsed - sleep_time)
-    # 0.25s margin is hopefully enough to account for any system overhead.
-    assert delta_to_expected < 0.25
+    assert elapsed >= sleep_time
+    if not u_boot_console.config.gdbserver:
+        # 0.25s margin is hopefully enough to account for any system overhead.
+        assert elapsed < (sleep_time + 0.25)
diff --git a/test/py/u_boot_console_base.py b/test/py/u_boot_console_base.py
index 392f8cb885..cc54273351 100644
--- a/test/py/u_boot_console_base.py
+++ b/test/py/u_boot_console_base.py
@@ -300,7 +300,8 @@ class ConsoleBase(object):
             # text if LCD is enabled. This value may need tweaking in the
             # future, possibly per-test to be optimal. This works for 'help'
             # on board 'seaboard'.
-            self.p.timeout = 30000
+            if not self.config.gdbserver:
+                self.p.timeout = 30000
             self.p.logfile_read = self.logstream
             if self.config.buildconfig.get('CONFIG_SPL', False) == 'y':
                 m = self.p.expect([pattern_u_boot_spl_signon] + self.bad_patterns)
diff --git a/test/py/u_boot_console_sandbox.py b/test/py/u_boot_console_sandbox.py
index a7263f30b8..3de0fe4a3b 100644
--- a/test/py/u_boot_console_sandbox.py
+++ b/test/py/u_boot_console_sandbox.py
@@ -39,7 +39,10 @@ class ConsoleSandbox(ConsoleBase):
             A u_boot_spawn.Spawn object that is attached to U-Boot.
         """
 
-        cmd = [
+        cmd = []
+        if self.config.gdbserver:
+            cmd += ['gdbserver', self.config.gdbserver]
+        cmd += [
             self.config.build_dir + '/u-boot',
             '-d',
             self.config.build_dir + '/arch/sandbox/dts/test.dtb'
diff --git a/test/py/u_boot_spawn.py b/test/py/u_boot_spawn.py
index 0f52d3e945..4b9e81af3e 100644
--- a/test/py/u_boot_spawn.py
+++ b/test/py/u_boot_spawn.py
@@ -148,10 +148,14 @@ class Spawn(object):
                     self.buf = self.buf[posafter:]
                     return earliest_pi
                 tnow_s = time.time()
-                tdelta_ms = (tnow_s - tstart_s) * 1000
-                if tdelta_ms > self.timeout:
-                    raise Timeout()
-                events = self.poll.poll(self.timeout - tdelta_ms)
+                if self.timeout:
+                    tdelta_ms = (tnow_s - tstart_s) * 1000
+                    poll_maxwait = self.timeout - tdelta_ms
+                    if tdelta_ms > self.timeout:
+                        raise Timeout()
+                else:
+                    poll_maxwait = None
+                events = self.poll.poll(poll_maxwait)
                 if not events:
                     raise Timeout()
                 c = os.read(self.fd, 1024)