diff --git a/smac/configspace/util.py b/smac/configspace/util.py
index 969c535e5..be5278390 100644
--- a/smac/configspace/util.py
+++ b/smac/configspace/util.py
@@ -8,5 +8,16 @@
 def impute_inactive_hyperparameters(configs: List[Configuration]) -> np.ndarray:
     configs_array = np.array([config.get_array() for config in configs],
                              dtype=np.float64)
-    configs_array[~np.isfinite(configs_array)] = -1
+    configuration_space = configs[0].configuration_space
+    for hp in configuration_space.get_hyperparameters():
+        default = hp._inverse_transform(hp.default)
+        idx = configuration_space.get_idx_by_hyperparameter_name(hp.name)
+
+        # Create a mask which is True for all non-finite entries in column idx!
+        column_mask = np.zeros(configs_array.shape, dtype=np.bool)
+        column_mask[:, idx] = True
+        nonfinite_mask = ~np.isfinite(configs_array)
+        mask = column_mask & nonfinite_mask
+
+        configs_array[mask] = default
     return configs_array
\ No newline at end of file
diff --git a/test/test_configspace/test_configspace.py b/test/test_configspace/test_configspace.py
index 3f5a1c7eb..75f91554f 100644
--- a/test/test_configspace/test_configspace.py
+++ b/test/test_configspace/test_configspace.py
@@ -7,6 +7,9 @@
 import unittest
 
 from ConfigSpace.io import pcs
+from ConfigSpace.hyperparameters import CategoricalHyperparameter
+from ConfigSpace.conditions import EqualsCondition
+import smac.configspace
 
 
 class ConfigSpaceTest(unittest.TestCase):
@@ -27,5 +30,21 @@ def test_spear(self):
             print(config.get_dictionary())
 
 
+    def test_impute_inactive_hyperparameters(self):
+        cs = smac.configspace.ConfigurationSpace()
+        a = cs.add_hyperparameter(CategoricalHyperparameter('a', [0, 1],
+                                                            default=0))
+        b = cs.add_hyperparameter(CategoricalHyperparameter('b', [0, 1],
+                                                            default=1))
+        cs.add_condition(EqualsCondition(b, a, 1))
+        cs.seed(1)
+        configs = cs.sample_configuration(size=100)
+        config_array = smac.configspace.impute_inactive_hyperparameters(configs)
+        for line in config_array:
+            if line[0] == 0:
+                self.assertEqual(line[1], 1)
+
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/test/test_smbo/test_smbo.py b/test/test_smbo/test_smbo.py
index d21042abc..9162aa736 100644
--- a/test/test_smbo/test_smbo.py
+++ b/test/test_smbo/test_smbo.py
@@ -211,7 +211,7 @@ def test_choose_next_empty_X_2(self):
         self.assertEqual(len(x), 1)
         self.assertIsInstance(x[0], Configuration)
 
-    @mock.patch('ConfigSpace.util.impute_inactive_values')
+    @mock.patch('smac.smbo.smbo.impute_inactive_hyperparameters')
     @mock.patch.object(EI, '__call__')
     @mock.patch.object(ConfigurationSpace, 'sample_configuration')
     def test_get_next_by_random_search_sorted(self,
@@ -221,7 +221,7 @@ def test_get_next_by_random_search_sorted(self,
         values = (10, 1, 9, 2, 8, 3, 7, 4, 6, 5)
         patch_sample.return_value = [ConfigurationMock(i) for i in values]
         patch_ei.return_value = np.array([[_] for _ in values], dtype=float)
-        patch_impute.side_effect = lambda x: x
+        patch_impute.side_effect = lambda l: values
         smbo = SMAC(self.scenario, rng=1).solver
         rval = smbo._get_next_by_random_search(10, True)
         self.assertEqual(len(rval), 10)
@@ -234,8 +234,7 @@ def test_get_next_by_random_search_sorted(self,
         # Check that config.get_array works as desired and imputation is used
         #  in between
         np.testing.assert_allclose(patch_ei.call_args[0][0],
-                                   np.array(values, dtype=float)
-                                   .reshape((-1, 1)))
+                                   np.array(values, dtype=float))
 
     @mock.patch.object(ConfigurationSpace, 'sample_configuration')
     def test_get_next_by_random_search(self, patch):