diff --git a/src/Mod/Fem/femsolver/elmer/sifio.py b/src/Mod/Fem/femsolver/elmer/sifio.py
index bd2ae98b39..28d615a7b8 100644
--- a/src/Mod/Fem/femsolver/elmer/sifio.py
+++ b/src/Mod/Fem/femsolver/elmer/sifio.py
@@ -394,12 +394,14 @@ class _Writer(object):
             return _TYPE_REAL
         if issubclass(dataType, str):
             return _TYPE_STRING
+        if issubclass(dataType, unicode):
+            return _TYPE_STRING
         raise ValueError("Unsupported data type: %s" % dataType)
 
     def _preprocess(self, data, dataType):
         if issubclass(dataType, Section):
             return str(self._idMgr.getId(data))
-        if issubclass(dataType, str):
+        if issubclass(dataType, str) or issubclass(dataType, unicode):
             return '"%s"' % data
         return str(data)