diff --git a/doctr/datasets/utils.py b/doctr/datasets/utils.py
index 77b0aceb4c..9b7d3f711b 100644
--- a/doctr/datasets/utils.py
+++ b/doctr/datasets/utils.py
@@ -111,10 +111,11 @@ def decode_sequence(
     """
     if not isinstance(input_seq, (Sequence, np.ndarray)):
         raise TypeError("Invalid sequence type")
-    if isinstance(input_seq, np.ndarray) and (
-        not np.issubdtype(input_seq.dtype, np.integer) or (input_seq.size > 0 and input_seq.max() >= len(mapping))
-    ):
-        raise AssertionError("Input must be an array of int, with max less than mapping size")
+    if isinstance(input_seq, np.ndarray) and not np.issubdtype(input_seq.dtype, np.integer):
+        raise AssertionError("Input must be an array of int, with values between 0 and the mapping size")
+    # A negative index would silently wrap around to the end of the mapping (e.g. an EOS of -1 read as a char)
+    if len(input_seq) > 0 and (min(input_seq) < 0 or max(input_seq) >= len(mapping)):
+        raise AssertionError("Input must be an array of int, with values between 0 and the mapping size")
 
     return "".join(map(mapping.__getitem__, input_seq))
 
diff --git a/tests/common/test_datasets_utils.py b/tests/common/test_datasets_utils.py
index 9343c48908..d48518e1ba 100644
--- a/tests/common/test_datasets_utils.py
+++ b/tests/common/test_datasets_utils.py
@@ -61,6 +61,13 @@ def test_decode_sequence():
         utils.decode_sequence(np.array([2, 10]), mapping)
     with pytest.raises(AssertionError):
         utils.decode_sequence(np.array([2, 4.5]), mapping)
+    # negative indices (such as the default EOS of -1) are not wrapped around to the last chars of the mapping
+    with pytest.raises(AssertionError):
+        utils.decode_sequence(np.array([2, -1]), mapping)
+    with pytest.raises(AssertionError):
+        utils.decode_sequence([2, -1], mapping)
+    with pytest.raises(AssertionError):
+        utils.decode_sequence([2, 10], mapping)
 
     assert utils.decode_sequence([3, 4, 3, 4], mapping) == "dede"
     assert utils.decode_sequence(np.array([3, 4, 3, 4], dtype=np.int64), mapping) == "dede"