diff --git a/tools/run_tests/port_server.py b/tools/run_tests/port_server.py
index 3b85486ebfe599732f38f1db2756db9b03edc2e4..14e82b601eadbef7062397a2c33c791bff43318c 100755
--- a/tools/run_tests/port_server.py
+++ b/tools/run_tests/port_server.py
@@ -42,7 +42,7 @@ import time
 # increment this number whenever making a change to ensure that
 # the changes are picked up by running CI servers
 # note that all changes must be backwards compatible
-_MY_VERSION = 5
+_MY_VERSION = 7
 
 
 if len(sys.argv) == 2 and sys.argv[1] == 'dump_version':
diff --git a/tools/run_tests/run_tests.py b/tools/run_tests/run_tests.py
index c78a120fc6569510842a59bab8999dea14fc6646..b8017e6fe94ea021ef855d25e8c6868144b11be6 100755
--- a/tools/run_tests/run_tests.py
+++ b/tools/run_tests/run_tests.py
@@ -744,7 +744,8 @@ def _start_port_server(port_server_port):
     running = False
   if running:
     current_version = int(subprocess.check_output(
-        [sys.executable, 'tools/run_tests/port_server.py', 'dump_version']))
+        [sys.executable, os.path.abspath('tools/run_tests/port_server.py'),
+         'dump_version']))
     print 'my port server is version %d' % current_version
     running = (version >= current_version)
     if not running:
@@ -755,13 +756,18 @@ def _start_port_server(port_server_port):
     fd, logfile = tempfile.mkstemp()
     os.close(fd)
     print 'starting port_server, with log file %s' % logfile
-    args = [sys.executable, 'tools/run_tests/port_server.py', '-p', '%d' % port_server_port, '-l', logfile]
+    args = [sys.executable, os.path.abspath('tools/run_tests/port_server.py'),
+            '-p', '%d' % port_server_port, '-l', logfile]
     env = dict(os.environ)
     env['BUILD_ID'] = 'pleaseDontKillMeJenkins'
     if platform.system() == 'Windows':
+      # Working directory of port server needs to be outside of Jenkins
+      # workspace to prevent file lock issues.
+      tempdir = tempfile.mkdtemp()
       port_server = subprocess.Popen(
           args,
           env=env,
+          cwd=tempdir,
           creationflags = 0x00000008, # detached process
           close_fds=True)
     else: