diff --git a/src/caosadvancedtools/table_json_conversion/convert.py b/src/caosadvancedtools/table_json_conversion/convert.py
index 4b02fa46a8e7a2426118cd987e5d84f906e2dfdb..7d8060c01095a4c7e7a5c68298ddd643e47d4d78 100644
--- a/src/caosadvancedtools/table_json_conversion/convert.py
+++ b/src/caosadvancedtools/table_json_conversion/convert.py
@@ -707,8 +707,6 @@ def _set_in_nested(mydict: dict, path: list, value: Any, prefix: list = [], skip
     return mydict
 
 
-# ToDo: Fix https://gitlab.indiscale.com/caosdb/src/caosdb-advanced-user-tools/-/issues/138
-#       and remove pylint disable
 def to_dict(xlsx: Union[str, BinaryIO], schema: Union[dict, str, TextIO],
             validate: Optional[bool] = None, strict: bool = False) -> dict:
     """Convert the xlsx contents to a dict, it must follow a schema.
@@ -733,9 +731,5 @@ def to_dict(xlsx: Union[str, BinaryIO], schema: Union[dict, str, TextIO],
     out: dict
       A dict representing the JSON with the extracted data.
     """
-    if validate:
-        raise NotImplementedError(
-            "For input validation implement "
-            "https://gitlab.indiscale.com/caosdb/src/caosdb-advanced-user-tools/-/issues/138")
     converter = XLSXConverter(xlsx, schema, strict=strict)
-    return converter.to_dict()
+    return converter.to_dict(validate=validate)
diff --git a/unittests/table_json_conversion/test_read_xlsx.py b/unittests/table_json_conversion/test_read_xlsx.py
index ff32c6b1203112c6931e98e55de5e4c981167452..5bee9297478d70cc806d0e6759e9b9f5a7f9cb53 100644
--- a/unittests/table_json_conversion/test_read_xlsx.py
+++ b/unittests/table_json_conversion/test_read_xlsx.py
@@ -53,9 +53,7 @@ Returns
 json: dict
   The result of the conversion.
     """
-    # FIXME Set default "validate" back to True, after implementation of
-    # https://gitlab.indiscale.com/caosdb/src/caosdb-advanced-user-tools/-/issues/138
-    result = convert.to_dict(xlsx=xlsx_file, schema=schema_file, validate=validate)
+    result = convert.to_dict(xlsx=xlsx_file, schema=schema_file, validate=True)
     if known_good_file:
         with open(known_good_file, encoding="utf-8") as myfile:
             expected = json.load(myfile)