diff --git a/lib/iris/tests/test_cdm.py b/lib/iris/tests/test_cdm.py
index 4047abd7e7..c5bb66a273 100644
--- a/lib/iris/tests/test_cdm.py
+++ b/lib/iris/tests/test_cdm.py
@@ -41,6 +41,7 @@
 import iris.coords
 import iris.cube
 import iris.fileformats
+import iris.fileformats.dot
 import iris.tests.pp as pp
 import iris.tests.stock