diff --git a/src/graphrelax/relaxer.py b/src/graphrelax/relaxer.py
index 3407ef3..6bb4357 100644
--- a/src/graphrelax/relaxer.py
+++ b/src/graphrelax/relaxer.py
@@ -449,7 +449,9 @@ def get_energy_breakdown(self, pdb_string: str) -> dict:
                 # Set this force to group i
                 force.setForceGroup(i)
 
-            # Recreate simulation with force groups
+            # Recreate simulation with force groups (need new integrator since
+            # the previous one is already bound to a context)
+            integrator = openmm.LangevinIntegrator(0, 0.01, 0.0)
             simulation = openmm_app.Simulation(
                 pdb.topology, system, integrator, platform
             )