diff --git a/src/qibo/models/variational.py b/src/qibo/models/variational.py
index de6cfbdc65..1fa040780b 100644
--- a/src/qibo/models/variational.py
+++ b/src/qibo/models/variational.py
@@ -78,12 +78,12 @@ def _loss(params, circuit, hamiltonian):
             for gate in self.circuit.queue:
                 _ = gate.cache
             loss = K.compile(_loss)
+        elif method != "sgd":
+            dtype = getattr(K.np, K._dtypes.get("DTYPE"))
+            loss = lambda p, c, h: dtype(K.to_numpy(_loss(p, c, h)))
         else:
             loss = _loss
 
-        if method != "sgd":
-            loss = lambda p, c, h: K.to_numpy(_loss(p, c, h))
-
         result, parameters, extra = self.optimizers.optimize(loss, initial_state,
                                                              args=(self.circuit, self.hamiltonian),
                                                              method=method, jac=jac, hess=hess, hessp=hessp,