diff --git a/PyNDN/SignedInfo.py b/PyNDN/SignedInfo.py
index 79c2f4f..cadf1e7 100644
--- a/PyNDN/SignedInfo.py
+++ b/PyNDN/SignedInfo.py
@@ -44,7 +44,7 @@
             args += ["keyLocator=%r" % self.keyLocator]
         if self.freshnessSeconds is not None:
             args += ["freshness=%r" % self.freshnessSeconds]
-        if self.timeStamp is not None:
+        if self.timestamp is not None:
             args += ["timestamp=%r" % self.timestamp]
         if self.type != CONTENT_DATA:
             args += ["type=%r" % self.type]