diff --git a/ipie/estimators/energy.py b/ipie/estimators/energy.py
index d8a6936b..cd7a7671 100644
--- a/ipie/estimators/energy.py
+++ b/ipie/estimators/energy.py
@@ -132,7 +132,7 @@ def __init__(
         self.ascii_filename = filename
 
     def compute_estimator(self, system, walkers, hamiltonian, trial, istep=1):
-        trial.calc_greens_function(walkers)
+        walkers.ovlp = trial.calc_greens_function(walkers)
         # Need to be able to dispatch here
         energy = local_energy(system, hamiltonian, walkers, trial)
         self._data["ENumer"] = xp.sum(walkers.weight * energy[:, 0].real)