diff --git a/tests/test_optim.py b/tests/test_optim.py
index aea935246f..5e0ce9338b 100644
--- a/tests/test_optim.py
+++ b/tests/test_optim.py
@@ -380,7 +380,7 @@ 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_minuit(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()
@@ -408,7 +408,7 @@ def test_optim_uncerts_minuit(backend, source, spec, mu):
 @pytest.mark.skip_numpy
 @pytest.mark.skip_numpy_minuit
 def test_optim_uncerts_autodiff(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()
@@ -438,7 +438,7 @@ def test_optim_uncerts_autodiff(backend, source, spec, mu):
 @pytest.mark.parametrize('mu', [1.0], ids=['mu=1'])
 @pytest.mark.only_numpy_minuit
 def test_optim_correlations_minuit(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()
@@ -470,7 +470,7 @@ def test_optim_correlations_minuit(backend, source, spec, mu):
 @pytest.mark.skip_numpy
 @pytest.mark.skip_numpy_minuit
 def test_optim_correlations_autodiff(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()