diff --git a/nanochat/gpt.py b/nanochat/gpt.py
index 0b717bb..3e12424 100644
--- a/nanochat/gpt.py
+++ b/nanochat/gpt.py
@@ -434,8 +434,8 @@ class GPT(nn.Module):
         self._ensure_rope_cache(T0 + T, device=idx.device)
 
         # Now it's safe to slice
-        assert idx.device == self.cos.device, f"RoPE buffers and idx device mismatch: {idx.device} != {self.cos.device}"
-        assert self.cos.dtype == torch.bfloat16, "RoPE buffers must be bfloat16"
+        assert idx.device == self.cos.device, f"Rotary embeddings and idx are on different devices: {idx.device} != {self.cos.device}"
+        assert self.cos.dtype == torch.bfloat16, "Rotary embeddings must be in bfloat16"
 
         cos_sin = self.cos[:, T0:T0+T], self.sin[:, T0:T0+T]