diff --git a/src/z3c/formdemo/addressbook/browser.py b/src/z3c/formdemo/addressbook/browser.py
index 04b31ec..7e2f48f 100644
--- a/src/z3c/formdemo/addressbook/browser.py
+++ b/src/z3c/formdemo/addressbook/browser.py
@@ -107,9 +107,9 @@ def update(self):
         self.addressForms = []
         for name, address in self.getContent().items():
             form = AddressForm(address, self.request, self.parentForm)
-            form.name = name
+            form.name = str(name)
             # The prefix is created at runtime to guarantee uniqueness
-            form.prefix = self.prefix + name + '.'
+            form.prefix = self.prefix + str(name) + '.'
             form.update()
             # Updating the address can also mean its deletion. If deleted, it
             # is not added to the list.
diff --git a/src/z3c/formdemo/spreadsheet/spreadsheet.py b/src/z3c/formdemo/spreadsheet/spreadsheet.py
index e1f3091..d1ea5fe 100644
--- a/src/z3c/formdemo/spreadsheet/spreadsheet.py
+++ b/src/z3c/formdemo/spreadsheet/spreadsheet.py
@@ -88,7 +88,7 @@ def __init__(self, spreadsheet, content):
         super(EditRow, self).__init__(spreadsheet.context, spreadsheet.request)
         self.fields = spreadsheet.rowFields
         self.content = content
-        self.prefix = content.__name__+'.'
+        self.prefix = str(content.__name__) + '.'
         self.sessionKey = spreadsheet.sessionKey
 
     @property