diff --git a/icartt/dataset.py b/icartt/dataset.py
index a283bc99b3544f80013acd258dc8a54457738cad..2b760476ecd0dab3ad3c569039231d6791223dc2 100644
--- a/icartt/dataset.py
+++ b/icartt/dataset.py
@@ -107,7 +107,7 @@ class Variable(collections.UserList):
         '''
         Return variable description string as it appears in an ICARTT file
         '''
-        return self.splitChar.join( [ self.name, self.units, self.longname ] )
+        return self.splitChar.join( [ str(self.name), str(self.units), str(self.longname) ] )
     
     def append(self, *argv):
         '''