diff --git a/benchmarks/magnetic_field_extrapolation/python_numpy/magnetic_field_extrapolation.py b/benchmarks/magnetic_field_extrapolation/python_numpy/magnetic_field_extrapolation.py
index 75f073dd..9cf17df5 100644
--- a/benchmarks/magnetic_field_extrapolation/python_numpy/magnetic_field_extrapolation.py
+++ b/benchmarks/magnetic_field_extrapolation/python_numpy/magnetic_field_extrapolation.py
@@ -66,7 +66,8 @@ def main():
 
     B.start()
     for _ in range(B.size[2]):
-        calcB(window(B_x0))
+        Rx, Ry, Rz = calcB(window(B_x0))
+        B.flush()
     B.stop()
     B.pprint()