diff --git a/tests/test_backend_consistency.py b/tests/test_backend_consistency.py
index 3a2bca22f3..512b06b707 100644
--- a/tests/test_backend_consistency.py
+++ b/tests/test_backend_consistency.py
@@ -99,7 +99,7 @@ def test_hypotest_qmu_tilde(
         else [signal_sample, background_sample]
     )
     spec = {'channels': [{'name': 'singlechannel', 'samples': samples}]}
-    pdf = pyhf.Model(spec)
+    pdf = pyhf.Model(spec, poi_name="mu")
 
     data = source['bindata']['data'] + pdf.config.auxdata
 
diff --git a/tests/test_optim.py b/tests/test_optim.py
index e4c5409076..b94b722cf8 100644
--- a/tests/test_optim.py
+++ b/tests/test_optim.py
@@ -312,7 +312,7 @@ def spec(source):
 
 @pytest.mark.parametrize('mu', [1.0], ids=['mu=1'])
 def test_optim(backend, source, spec, mu):
-    pdf = pyhf.Model(spec)
+    pdf = pyhf.Model(spec, poi_name="mu")
     data = source['bindata']['data'] + pdf.config.auxdata
 
     init_pars = pdf.config.suggested_init()
@@ -336,7 +336,7 @@ def test_optim(backend, source, spec, mu):
 
 @pytest.mark.parametrize('mu', [1.0], ids=['mu=1'])
 def test_optim_with_value(backend, source, spec, mu):
-    pdf = pyhf.Model(spec)
+    pdf = pyhf.Model(spec, poi_name="mu")
     data = source['bindata']['data'] + pdf.config.auxdata
 
     init_pars = pdf.config.suggested_init()
@@ -364,7 +364,7 @@ def test_optim_with_value(backend, source, spec, mu):
 @pytest.mark.parametrize('mu', [1.0], ids=['mu=1'])
 @pytest.mark.only_numpy_minuit
 def test_optim_uncerts(backend, source, spec, mu):
-    pdf = pyhf.Model(spec)
+    pdf = pyhf.Model(spec, poi_name="mu")
     data = source['bindata']['data'] + pdf.config.auxdata
 
     init_pars = pdf.config.suggested_init()
@@ -391,7 +391,7 @@ def test_optim_uncerts(backend, source, spec, mu):
 @pytest.mark.parametrize('mu', [1.0], ids=['mu=1'])
 @pytest.mark.only_numpy_minuit
 def test_optim_correlations(backend, source, spec, mu):
-    pdf = pyhf.Model(spec)
+    pdf = pyhf.Model(spec, poi_name="mu")
     data = source['bindata']['data'] + pdf.config.auxdata
 
     init_pars = pdf.config.suggested_init()
diff --git a/tests/test_validation.py b/tests/test_validation.py
index 37d7500de1..1e3b54392b 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -788,7 +788,9 @@ def test_validation(setup):
     source = setup['source']
 
     pdf = pyhf.Model(
-        setup['spec'], modifier_settings={'normsys': {'interpcode': 'code1'}}
+        setup["spec"],
+        modifier_settings={"normsys": {"interpcode": "code1"}},
+        poi_name="mu",
     )
 
     if 'channels' in source: