diff --git a/casanovo/denovo/model.py b/casanovo/denovo/model.py
index 88f3aaca..716dd747 100644
--- a/casanovo/denovo/model.py
+++ b/casanovo/denovo/model.py
@@ -2,6 +2,7 @@
 
 import collections
 import heapq
+import itertools
 import logging
 import warnings
 from pathlib import Path
@@ -1062,10 +1063,11 @@ def predict_step(
                 batch_aa_scores,
                 psm_batch[3],
             ):
+                spectrum_i = tuple(spectrum_i)
                 predictions_all[spectrum_i].append(
                     ms_io.PepSpecMatch(
                         sequence=peptide,
-                        spectrum_id=tuple(spectrum_i),
+                        spectrum_id=spectrum_i,
                         peptide_score=peptide_score,
                         charge=int(charge),
                         calc_mz=self.peptide_mass_calculator.mass(
@@ -1079,16 +1081,20 @@ def predict_step(
                     )
                 )
         # Filter the top-scoring prediction(s) for each spectrum.
-        predictions = [
-            *(
-                sorted(
-                    spectrum_predictions,
-                    key=lambda p: p.peptide_score,
-                    reverse=True,
-                )[: self.top_match]
-                for spectrum_predictions in predictions_all.values()
+        predictions = list(
+            itertools.chain.from_iterable(
+                [
+                    *(
+                        sorted(
+                            spectrum_predictions,
+                            key=lambda p: p.peptide_score,
+                            reverse=True,
+                        )[: self.top_match]
+                        for spectrum_predictions in predictions_all.values()
+                    )
+                ]
             )
-        ]
+        )
         return predictions
 
     def on_predict_batch_end(