diff --git a/pmda/parallel.py b/pmda/parallel.py
index 361edc4..69ee1b2 100644
--- a/pmda/parallel.py
+++ b/pmda/parallel.py
@@ -396,7 +396,7 @@ def run(self,
                 res = [([], [], [], 0, wait_start, 0, 0)]
             # record conclude time
             with timeit() as conclude:
-                self._results = np.asarray([el[0] for el in res])
+                self._results = [el[0] for el in res]
                 # save the frame numbers for all blocks
                 self._blocks = _blocks
                 self._conclude()