diff --git a/tests/test_client.py b/tests/test_client.py
index 59f822e..623c8a8 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -638,7 +638,7 @@ class TestTransportUsage:
         xsd_content = '<xsd:element name="Data" type="xsd:string"/>'
         web_service_URL = "Great minds think alike"
         xsd_target_namespace = "omicron psi"
-        wsdl = testutils.wsdl(b(xsd_content), operation_name="pi",
+        wsdl = testutils.wsdl(xsd_content, operation_name="pi",
             xsd_target_namespace=xsd_target_namespace, input="Data",
             output="Data", web_service_URL=web_service_URL)
         test_input_data = "Riff-raff"
diff --git a/tests/testutils/__init__.py b/tests/testutils/__init__.py
index 0062a90..923855d 100644
--- a/tests/testutils/__init__.py
+++ b/tests/testutils/__init__.py
@@ -23,6 +23,8 @@ Package containing different utilities used for suds project testing.
 import suds.client
 import suds.store
 
+import six
+
 import os
 import subprocess
 import sys
@@ -153,6 +155,8 @@ def wsdl(schema_content, input=None, output=None, operation_name="f",
         name.
 
     """
+    assert isinstance(schema_content, six.string_types)
+
     has_input = input is not None
     has_output = output is not None