diff --git a/tests/functional/pyocf/types/cache.py b/tests/functional/pyocf/types/cache.py
index c087bf4..eedd278 100644
--- a/tests/functional/pyocf/types/cache.py
+++ b/tests/functional/pyocf/types/cache.py
@@ -300,6 +300,8 @@ class Cache:
         c.wait()
         self.write_unlock()
 
+        self.device = None
+
         if c.results["error"]:
             raise OcfError("Failed to detach failover cache device", c.results["error"])