diff --git a/common/rfb/SMsgWriter.cxx b/common/rfb/SMsgWriter.cxx
index cf3264e..bc3f439 100644
--- a/common/rfb/SMsgWriter.cxx
+++ b/common/rfb/SMsgWriter.cxx
@@ -101,7 +101,9 @@
   os->writeU32(flags);
 
   os->writeU8(len);
-  os->writeBytes(data, len);
+
+  if (len > 0)
+    os->writeBytes(data, len);
 
   endMsg();
 }
diff --git a/common/rfb/VNCSConnectionST.cxx b/common/rfb/VNCSConnectionST.cxx
index 0a2ca33..d2206f9 100644
--- a/common/rfb/VNCSConnectionST.cxx
+++ b/common/rfb/VNCSConnectionST.cxx
@@ -666,6 +666,7 @@
       fenceFlags = flags & (fenceFlagBlockBefore | fenceFlagBlockAfter | fenceFlagSyncNext);
       fenceDataLen = len;
       delete [] fenceData;
+      fenceData = NULL;
       if (len > 0) {
         fenceData = new char[len];
         memcpy(fenceData, data, len);