diff --git a/dev/buildbot/master/master.cfg b/dev/buildbot/master/master.cfg
index 42887660..21dba74b 100644
--- a/dev/buildbot/master/master.cfg
+++ b/dev/buildbot/master/master.cfg
@@ -111,7 +111,7 @@ def python_slave(key, platform, cmake_args = [], cmake_env = {}, build_args = []
     # property set? If so, clobber the checkout folders.
     if platform.startswith('win'):
         # del /q destination\* && for /d %x in (destination\*) do @rd /s /q %x
-        cmd = ['echo', WithProperties('%(fullclean:-no)s')]
+        cmd = ['echo', WithProperties('if %(fullclean:-no)s == yes (echo yes) ELSE (echo no)')]
     else:
         cmd = ['bash', '-c',
            WithProperties('if [ %(fullclean:-no)s == yes ]; then echo pwd; rm -rfv *; echo fully cleaned; fi'),