diff --git a/pypolychord/polychord.py b/pypolychord/polychord.py
index 76ba3862..a040ac72 100644
--- a/pypolychord/polychord.py
+++ b/pypolychord/polychord.py
@@ -553,7 +553,9 @@ def run(loglikelihood, nDims, **kwargs):
         'nlives': {},
         'seed': -1,
     }
-    default_kwargs['grade_frac'] = [1.0]*len(default_kwargs['grade_dims'])
+    default_kwargs['grade_frac'] = ([1.0]*len(default_kwargs['grade_dims'])
+                                    if 'grade_dims' not in kwargs else
+                                    [1.0]*len(kwargs['grade_dims']))
 
     if not set(kwargs.keys()) <= set(default_kwargs.keys()):
         raise TypeError(f"{__name__} got unknown keyword arguments: "
diff --git a/tests/test_run_pypolychord.py b/tests/test_run_pypolychord.py
index d9181a86..6852da37 100644
--- a/tests/test_run_pypolychord.py
+++ b/tests/test_run_pypolychord.py
@@ -121,11 +121,10 @@ def no_derived_gaussian_likelihood(theta):
 
 def test_grade_dims():
     grade_dims = [1, 3]
-    grade_frac = [0.5, 0.5]
     pypolychord.run(gaussian_likelihood, 4, nDerived=1,
                     prior=uniform_prior, read_resume=False,
-                    grade_dims=grade_dims, grade_frac=grade_frac)
+                    grade_dims=grade_dims)
     with pytest.raises(ValueError):
         pypolychord.run(gaussian_likelihood, 5, nDerived=1,
                         prior=uniform_prior, read_resume=False,
-                        grade_dims=grade_dims, grade_frac=grade_frac)
+                        grade_dims=grade_dims)