diff --git a/sc2ts/inference.py b/sc2ts/inference.py
index c22d358..387f7d8 100644
--- a/sc2ts/inference.py
+++ b/sc2ts/inference.py
@@ -568,12 +568,12 @@ def extend(
         f"mutations={base_ts.num_mutations};date={base_ts.metadata['sc2ts']['date']}"
     )
 
-    metadata_matches = list(metadata_db.get(date))
+    metadata_matches = {md["strain"]: md for md in metadata_db.get(date)}
 
     logger.info(f"Got {len(metadata_matches)} metadata matches")
 
     preprocessed_samples = preprocess(
-        strains=[md["strain"] for md in metadata_matches],
+        strains=list(metadata_matches.keys()),
         alignment_store_path=alignment_store.path,
         keep_sites=base_ts.sites_position.astype(int),
         progress_title=date,
@@ -584,10 +584,11 @@ def extend(
     pango_lineage_key = "Viridian_pangolin"
 
     samples = []
-    for s, md in zip(preprocessed_samples, metadata_matches):
+    for s in preprocessed_samples:
         if s.haplotype is None:
             logger.debug(f"No alignment stored for {s.strain}")
             continue
+        md = metadata_matches[s.strain]
         s.metadata = md
         s.pango = md.get(pango_lineage_key, "Unknown")
         s.date = date
@@ -1270,7 +1271,6 @@ def mutation_summary(self):
         return "[" + ", ".join(str(mutation) for mutation in self.mutations) + "]"
 
 
-
 def get_match_info(ts, sample_paths, sample_mutations):
     tables = ts.tables
     assert np.all(tables.sites.ancestral_state_offset == np.arange(ts.num_sites + 1))