diff --git a/polyfile/magic.py b/polyfile/magic.py
index a0ecb87..02650eb 100644
--- a/polyfile/magic.py
+++ b/polyfile/magic.py
@@ -2600,7 +2600,7 @@ def test(self, data: bytes, absolute_offset: int, parent_match: Optional[TestRes
             detector.feed(data[offset:offset+1024])
             offset += 1024
         detector.close()
-        if detector.result["confidence"] >= self.minimum_encoding_confidence:
+        if detector.result["confidence"] >= self.minimum_encoding_confidence and detector.result["encoding"] is not None:
             encoding = detector.result["encoding"]
             try:
                 value = data[absolute_offset:].decode(encoding)