diff --git a/tests/test_project.py b/tests/test_project.py
index 67bebd3e3..7d2990a53 100644
--- a/tests/test_project.py
+++ b/tests/test_project.py
@@ -2538,9 +2538,9 @@ class A(FlowProject):
         def op(job):
             pass
 
-        assert len(A._OPERATION_HOOK_REGISTRY[op]["on_start"])
-        assert len(A._OPERATION_HOOK_REGISTRY[op]["on_success"])
-        assert len(A._OPERATION_HOOK_REGISTRY[op]["on_exception"])
+        assert len(A._OPERATION_HOOK_REGISTRY[op]["on_start"]) == 1
+        assert len(A._OPERATION_HOOK_REGISTRY[op]["on_success"]) == 1
+        assert len(A._OPERATION_HOOK_REGISTRY[op]["on_exception"]) == 1
 
         @track.install_operation_hooks(A)
         @A.operation