diff --git a/src/testlink/testlinkhelper.py b/src/testlink/testlinkhelper.py
index 81da330..d395cec 100644
--- a/src/testlink/testlinkhelper.py
+++ b/src/testlink/testlinkhelper.py
@@ -96,7 +96,7 @@ def _setParamsFromEnv(self):
         if self._devkey is None:
             self._devkey = os.getenv(self.ENVNAME_DEVKEY, self.DEFAULT_DEVKEY)
 
-        if not self._proxy:
+        if self._proxy is None:
             self._proxy =  os.getenv(self.ENVNAME_PROXY, self.DEFAULT_PROXY)
 
     def _createArgparser(self, usage):