diff --git a/src/lib/python/isc/ddns/session.py b/src/lib/python/isc/ddns/session.py
index d36f6fd..0effde0 100644
--- a/src/lib/python/isc/ddns/session.py
+++ b/src/lib/python/isc/ddns/session.py
@@ -792,9 +792,9 @@ class UpdateSession:
         # serial magic and add the newly created one
 
         # get it from DS and to increment and stuff
-        result, old_soa, _ = self.__finder.find(self.__zname, RRType.SOA(),
-                                                ZoneFinder.NO_WILDCARD |
-                                                ZoneFinder.FIND_GLUE_OK)
+        result, old_soa, _ = self.__diff.find(self.__zname, RRType.SOA(),
+                                              ZoneFinder.NO_WILDCARD |
+                                              ZoneFinder.FIND_GLUE_OK)
         # We may implement recovering from missing SOA data at some point, but
         # for now servfail on such a broken state
         if result != ZoneFinder.SUCCESS:
diff --git a/src/lib/python/isc/ddns/tests/session_tests.py b/src/lib/python/isc/ddns/tests/session_tests.py
index f191995..cb53c7a 100644
--- a/src/lib/python/isc/ddns/tests/session_tests.py
+++ b/src/lib/python/isc/ddns/tests/session_tests.py
@@ -1273,23 +1273,23 @@ class SessionTest(SessionTestBase):
         self.check_full_handle_result(Rcode.NOERROR(),
                                       [ self.rrset_update_del_soa_apex,
                                         self.rrset_update_soa_del ])
-        self.check_inzone_data(isc.datasrc.ZoneFinder.SUCCESS,
-                               isc.dns.Name("example.org"),
-                               RRType.SOA(),
-                               incremented_soa_rrset_01)
+        self.__check_inzone_data(isc.datasrc.ZoneFinder.SUCCESS,
+                                 isc.dns.Name("example.org"),
+                                 RRType.SOA(),
+                                 incremented_soa_rrset_01)
 
         # If we delete everything at the apex, the SOA and NS rrsets should be
         # untouched (but serial will be incremented)
         self.check_full_handle_result(Rcode.NOERROR(),
                                       [ self.rrset_update_del_name_apex ])
-        self.check_inzone_data(isc.datasrc.ZoneFinder.SUCCESS,
-                               isc.dns.Name("example.org"),
-                               RRType.SOA(),
-                               incremented_soa_rrset_02)
-        self.check_inzone_data(isc.datasrc.ZoneFinder.SUCCESS,
-                               isc.dns.Name("example.org"),
-                               RRType.NS(),
-                               orig_ns_rrset)
+        self.__check_inzone_data(isc.datasrc.ZoneFinder.SUCCESS,
+                                 isc.dns.Name("example.org"),
+                                 RRType.SOA(),
+                                 incremented_soa_rrset_02)
+        self.__check_inzone_data(isc.datasrc.ZoneFinder.SUCCESS,
+                                 isc.dns.Name("example.org"),
+                                 RRType.NS(),
+                                 orig_ns_rrset)
         # but the MX should be gone
         self.__check_inzone_data(isc.datasrc.ZoneFinder.NXRRSET,
                                  isc.dns.Name("example.org"),