diff --git a/buildbot/master.cfg b/buildbot/master.cfg
index bbe8bbad..b9d6a163 100644
--- a/buildbot/master.cfg
+++ b/buildbot/master.cfg
@@ -114,7 +114,7 @@ def makeBuildFactory(wxport, py_ver, build_type='basic'):
                               method=method
                               ))
 
-    cmd = [PYTHON, '-m', 'pip', 'install', '-r', 'requirements.txt']
+    cmd = [PYTHON, '-m', 'pip', 'install', '-U', '-r', 'requirements.txt']
     factory.addStep(
         steps.ShellCommand(name='install python packages', command=cmd, env=environ))