diff --git a/.gitignore b/.gitignore
index b5c3114..e0018ad 100644
--- a/.gitignore
+++ b/.gitignore
@@ -156,4 +156,4 @@ Thumbs.db
 # Common editor files
 *~
 *.swp
-_scratch/
\ No newline at end of file
+_scratch/
diff --git a/src/dask_ngs/_index.py b/src/dask_ngs/_index.py
index 8f6a3cb..10bfd20 100644
--- a/src/dask_ngs/_index.py
+++ b/src/dask_ngs/_index.py
@@ -10,6 +10,7 @@
 COMPRESSED_POSITION_SHIFT = 16
 UNCOMPRESSED_POSITION_MASK = 0xFFFF
 BLOCKSIZE = 65536
+BAM_PSEUDO_BIN = 37450
 
 
 def read_bai(path: str):
@@ -36,7 +37,7 @@ def read_bai(path: str):
                 # bin number
                 bin_id = int.from_bytes(f.read(4), **int_kwargs)
 
-                if bin_id == 37450:
+                if bin_id == BAM_PSEUDO_BIN:
                     # This is an entry that describes the "pseudo-bin" for the
                     # reference, using the same byte layout as normal bins but
                     # interpreted differently.