diff --git a/ietf/tests.py b/ietf/tests.py
index 3b5ad9cbe..9a2fc800e 100644
--- a/ietf/tests.py
+++ b/ietf/tests.py
@@ -191,7 +191,7 @@ class UrlTestCase(TestCase):
                                     # discard them too
                                     diff = ""
                                 if diff:
-                                    dfile = "%s/../test/diff/%s" % (settings.BASE_DIR, url.replace("/", "_"))
+                                    dfile = "%s/../test/diff/%s" % (settings.BASE_DIR, url.replace("/", "_").replace("?", "_"))
                                     if os.path.exists(dfile):
                                         dfile = open(dfile)
                                         #print "Reading OK diff file:", dfile.name
diff --git a/test/diff/_ipr_search__option=document_search&id_document_tag=2220 b/test/diff/_ipr_search__option=document_search&id_document_tag=2220
new file mode 100644
index 000000000..15e1780e8
--- /dev/null
+++ b/test/diff/_ipr_search__option=document_search&id_document_tag=2220
@@ -0,0 +1,31 @@
+--- https://datatracker.ietf.org/public/ipr_search.cgi?option=document_search&id_document_tag=2220 
++++ /ipr/search/?option=document_search&id_document_tag=2220 
+@@ -52,0 +52,6 @@
++Search result on draft-ietf-mobileip-protocol, "IP Mobility Support",
++that was published as RFC2002, "IP Mobility Support"
++
++No IPR disclosures related to draft-ietf-mobileip-protocol have been
++submitted
++
+@@ -56,0 +62,7 @@
++
++Search result on draft-ietf-mobileip-rfc2002-bis, "IP Mobility Support
++for IPv4, revised", that was published as RFC3220, "IP Mobility
++Support for IPv4, revised"
++
++No IPR disclosures related to draft-ietf-mobileip-rfc2002-bis have
++been submitted
+@@ -65,13 +78,0 @@
+-Search result on draft-ietf-mobileip-rfc2002-bis, "IP Mobility Support
+-for IPv4, revised", that was published as RFC3220, "IP Mobility
+-Support for IPv4, revised"
+-
+-No IPR disclosures related to draft-ietf-mobileip-rfc2002-bis have
+-been submitted
+-
+-Search result on draft-ietf-mobileip-protocol, "IP Mobility Support",
+-that was published as RFC2002, "IP Mobility Support"
+-
+-No IPR disclosures related to draft-ietf-mobileip-protocol have been
+-submitted
+-
\ No newline at end of file