diff --git a/src/common/GnuPG.py b/src/common/GnuPG.py
index 28b9c2987..bb6753fca 100644
--- a/src/common/GnuPG.py
+++ b/src/common/GnuPG.py
@@ -138,7 +138,7 @@ else:
 		def verify(self, str, sign):
 			if not USE_GPG:
 				return str
-			if not str:
+			if str == None:
 				return ''
 			f = tmpfile()
 			fd = f.fileno()