diff --git a/OpenSSL/test/test_ssl.py b/OpenSSL/test/test_ssl.py
index f645ad5..eef9cea 100644
--- a/OpenSSL/test/test_ssl.py
+++ b/OpenSSL/test/test_ssl.py
@@ -686,7 +686,7 @@
             fObj.write(dump_certificate(FILETYPE_PEM, cert).decode('ascii'))
             fObj.close()
             fObj = open(name.replace('pem', 'asn1'), 'w')
-            fObj.write(dump_certificate(FILETYPE_ASN1, cert))
+            fObj.write(dump_certificate(FILETYPE_ASN1, cert).decode('ascii'))
             fObj.close()
 
         for key, name in [(cakey, 'ca.key'), (ikey, 'i.key'), (skey, 's.key')]: