diff --git a/tests/test_octodns_source_axfr.py b/tests/test_octodns_source_axfr.py
index f808166..a1d2e1c 100644
--- a/tests/test_octodns_source_axfr.py
+++ b/tests/test_octodns_source_axfr.py
@@ -45,12 +45,12 @@ class TestAxfrSource(TestCase):
 
 class TestZoneFileSource(TestCase):
     source = ZoneFileSource('test', './tests/zones')
-    source_extension = ZoneFileSource('test', './tests/zones', 'extension')
 
     def test_zonefiles_with_extension(self):
+        source = ZoneFileSource('test', './tests/zones', 'extension')
         # Load zonefiles with a specified file extension
-        valid = Zone('unit.tests.', [])
-        self.source_extension.populate(valid)
+        valid = Zone('ext.unit.tests.', [])
+        source.populate(valid)
         self.assertEquals(1, len(valid.records))
 
     def test_populate(self):
diff --git a/tests/zones/unit.tests.extension b/tests/zones/ext.unit.tests.extension
similarity index 61%
rename from tests/zones/unit.tests.extension
rename to tests/zones/ext.unit.tests.extension
index 2821d9a..2ed7ac6 100644
--- a/tests/zones/unit.tests.extension
+++ b/tests/zones/ext.unit.tests.extension
@@ -1,5 +1,5 @@
-$ORIGIN unit.tests.
-@           3600 IN	SOA	ns1.unit.tests. root.unit.tests. (
+$ORIGIN ext.unit.tests.
+@           3600 IN	SOA	ns1.ext.unit.tests. root.ext.unit.tests. (
                         2018071501		; Serial
                         3600    ; Refresh (1 hour)
                         600     ; Retry (10 minutes)
@@ -8,5 +8,5 @@ $ORIGIN unit.tests.
                     )
 
 ; NS Records
-@           3600  IN  NS  ns1.unit.tests.
-@           3600  IN  NS  ns2.unit.tests.
+@           3600  IN  NS  ns1.ext.unit.tests.
+@           3600  IN  NS  ns2.ext.unit.tests.