diff --git a/src/abaco/ABaCo.py b/src/abaco/ABaCo.py
index 60c83d8..675c3f5 100644
--- a/src/abaco/ABaCo.py
+++ b/src/abaco/ABaCo.py
@@ -4418,11 +4418,22 @@ def fit(
         adv_lr=1e-3,
     ):
         # Define optimizer
+        if isinstance(self.vae.prior, MoCPPrior):
+            prior_params = self.vae.prior.parameters()
+
+        elif isinstance(self.vae.prior, VMMPrior):
+            prior_params = [self.vae.prior.u, self.vae.prior.var]
+
+        else:
+            raise NotImplementedError(
+                "metaABaCo prior distribution can only be 'MoG' or 'VMM'"
+            )
+
         vae_optimizer_1 = torch.optim.Adam(
             [
                 {"params": self.vae.encoder.parameters()},
                 {"params": self.vae.decoder.parameters()},
-                {"params": self.vae.prior.parameters()},
+                {"params": prior_params},
             ],
             lr=phase_1_vae_lr,
         )