diff --git a/AA_stat/localization.py b/AA_stat/localization.py
index f2c5347..79e4a52 100644
--- a/AA_stat/localization.py
+++ b/AA_stat/localization.py
@@ -150,7 +150,19 @@ def preprocess_spectrum(reader, spec_id, kwargs, acc=0.01):
         # logger.debug('Returning cached spectrum %s', spec_id)
         return spectrum
     # logger.debug('Preprocessing new spectrum %s', spec_id)
-    original = reader[spec_id]
+    try:
+        original = reader[spec_id]
+    except KeyError:
+        import re
+        match = re.search(r"scan=(\d+)", str(spec_id))
+        if match:
+            scan_num = match.group(1)
+            try:
+                original = reader[f"scan={scan_num}"]
+            except KeyError:
+                original = reader[scan_num]
+        else:
+            raise
     maxpeaks = kwargs.get('maxpeaks', 100)
     dynrange = kwargs.get('dynrange', 1000)