diff --git a/TM/io.py b/TM/io.py
index f744caac5dce93202d14ff432bb9f9496693b6c4..8b05f42586ff61a7cfb2311407bf21106fa935ba 100644
--- a/TM/io.py
+++ b/TM/io.py
@@ -1118,7 +1118,7 @@ def preload_chunk(chunkId, chunkTime, chunkLength, raw=True, processed=True, std
 
         for tr in chunkStream:
             # Check if there are STEIM2-incompatible values
-            diff_limit = np.iinfo(np.int32).max
+            diff_limit = np.iinfo(np.int32).max // 4
             if np.abs(np.diff(tr.data.astype(np.float32))).max() >= diff_limit:
                 encoding = 'STEIM1'  # or INT32, or FLOAT32
                 break  # Don't test the other traces