diff --git a/src/python/espressomd/magnetostatics.py b/src/python/espressomd/magnetostatics.py
index bfe30d2e3c..a43e19a84d 100644
--- a/src/python/espressomd/magnetostatics.py
+++ b/src/python/espressomd/magnetostatics.py
@@ -160,7 +160,7 @@ def validate_params(self, params):
             raise TypeError("Parameter 'tune' has to be a boolean")
 
     def required_keys(self):
-        return {"accuracy"}
+        return {"prefactor", "accuracy"}
 
     def default_params(self):
         return {"cao": -1,
diff --git a/testsuite/python/dipolar_interface.py b/testsuite/python/dipolar_interface.py
index 22cc14e905..636fd6c95b 100644
--- a/testsuite/python/dipolar_interface.py
+++ b/testsuite/python/dipolar_interface.py
@@ -128,6 +128,10 @@ def test_exceptions_p3m(self):
         MDLC = espressomd.magnetostatics.DLC
         dp3m_params = dict(prefactor=1., epsilon=0.1, accuracy=1e-6,
                            mesh=[49, 49, 49], cao=7, r_cut=4.5, alpha=0.9)
+        with self.assertRaisesRegex(RuntimeError, "Parameter 'prefactor' is missing"):
+            espressomd.magnetostatics.DipolarP3M(
+                **{key: value for key, value in dp3m_params.items()
+                   if key != 'prefactor'})
         with self.assertRaisesRegex(ValueError, "Parameter 'prefactor' must be > 0"):
             espressomd.magnetostatics.DipolarP3M(
                 **{**dp3m_params, 'prefactor': -2.})