diff --git a/filetype/utils.py b/filetype/utils.py
index e5f2a07..74af6ac 100644
--- a/filetype/utils.py
+++ b/filetype/utils.py
@@ -50,7 +50,10 @@ def get_bytes(obj):
         TypeError: if obj is not a supported type.
     """
     try:
-        obj = obj.read(_NUM_SIGNATURE_BYTES)
+        start_pos = obj.tell()
+        read_bytes = obj.read(_NUM_SIGNATURE_BYTES)
+        obj.seek(start_pos)
+        obj = read_bytes
     except AttributeError:
         # duck-typing as readable failed - we'll try the other options
         pass