diff --git a/conllu/parser.py b/conllu/parser.py
index 16ec94b..7456879 100644
--- a/conllu/parser.py
+++ b/conllu/parser.py
@@ -141,7 +141,7 @@ def parse_id_value(value):
 
 
 ANY_ID = re.compile(ID_SINGLE.pattern + "|" + ID_RANGE.pattern + "|" + ID_DOT_ID.pattern)
-DEPS_RE = re.compile("(" + ANY_ID.pattern + r"):[a-z][a-z_-]*(\:[a-z][a-z_-]*)?")
+DEPS_RE = re.compile("(" + ANY_ID.pattern + r"):[a-zA-Z][a-zA-Z0-9_-]*(\:[a-zA-Z][a-zA-Z0-9_-]*)?")
 MULTI_DEPS_PATTERN = re.compile(r"{}(\|{})*".format(DEPS_RE.pattern, DEPS_RE.pattern))
 
 def parse_paired_list_value(value):

diff --git a/tests/test_parser.py b/tests/test_parser.py
index 0e13a77..2733b58 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -361,6 +361,14 @@ class TestParsePairedListValue(unittest.TestCase):
             parse_paired_list_value("5:conj:and|8.1:nsubj:pass|9:nsubj:xsubj"),
             [("conj:and", 5), ("nsubj:pass", (8, ".", 1)), ("nsubj:xsubj", 9)]
         )
+        self.assertEqual(
+            parse_paired_list_value("1:compound|6:ARG|9:ARG1|10:ARG2"),
+            [('compound', 1), ('ARG', 6), ('ARG1', 9), ('ARG2', 10)]
+        )
+        self.assertNotEqual(
+            parse_paired_list_value("1:compound|6:ARG|9:ARG1|10:2ARG"),
+            [('compound', 1), ('ARG', 6), ('ARG1', 9), ('2ARG', 10)]
+        )
 
     def test_parse_empty(self):
         testcases = [

Column 'deps' is not being parsed most of the time
Given the following sentence:

```
Removed.
```

The code at `parser.py:152` looks like this:

```python
def parse_paired_list_value(value):
    if fullmatch(MULTI_DEPS_PATTERN, value):
        return [
            (part.split(":", 1)[1], parse_id_value(part.split(":")[0]))
            for part in value.split("|")
        ]

    return parse_nullable_value(value)
```

Is seems like the definition of `MULTI_DEPS_PATTERN` is not correct. Most `deps` values are returned as strings instead of a list of tuples, because the parsing fails. For example `'1:compound|6:ARG1|9:ARG1'` is considered bad, but according to [the specification](https://universaldependencies.org/format.html#syntactic-annotation) this should be alright. Actually the code for parsing inside of the if-statement works perfectly on this line. `'4:ARG1'` is also being considered flawed, but `'5:measure'` is being considered okay.
tests/test_parser.py::TestParsePairedListValue::test_parse_paired_list
tests/test_parser.py::TestParseLine::test_parse_line_nullable_fields tests/test_parser.py::TestParseLine::test_parse_line_with_spaces tests/test_parser.py::TestParseLine::test_parse_line_only_id_head tests/test_parser.py::TestParseLine::test_parse_line_without_spacing tests/test_parser.py::TestParseLine::test_parse_line_fewer_columns tests/test_parser.py::TestParseLine::test_parse_line tests/test_parser.py::TestParseLine::test_empty tests/test_parser.py::TestParseLine::test_parse_line_two_spaces tests/test_parser.py::TestParseDictValue::test_parse_dict_value tests/test_parser.py::TestParseIDValue::test_decimal tests/test_parser.py::TestParseIDValue::test_range tests/test_parser.py::TestParseIDValue::test_none tests/test_parser.py::TestParseIDValue::test_single tests/test_parser.py::TestHeadToToken::test_simple tests/test_parser.py::TestHeadToToken::test_decimal_ids_ignored tests/test_parser.py::TestHeadToToken::test_range_ids_ignored tests/test_parser.py::TestHeadToToken::test_missing_head tests/test_parser.py::TestHeadToToken::test_negative_head tests/test_parser.py::TestSerializeField::test_tuple tests/test_parser.py::TestSerializeField::test_string tests/test_parser.py::TestSerializeField::test_list tests/test_parser.py::TestSerializeField::test_ordered_dict tests/test_parser.py::TestSerializeField::test_none tests/test_parser.py::TestParseIntValue::test_parse_int_value tests/test_parser.py::TestParseTokenAndMetadata::test_invalid_metadata tests/test_parser.py::TestParseTokenAndMetadata::test_newlines_in_sentence tests/test_parser.py::TestParseTokenAndMetadata::test_custom_field_parsers tests/test_parser.py::TestParseTokenAndMetadata::test_empty tests/test_parser.py::TestParseTokenAndMetadata::test_custom_fields tests/test_parser.py::TestParseTokenAndMetadata::test_default_field_parsers_when_undefined tests/test_parser.py::TestParseNullableValue::test_parse_nullable_value tests/test_parser.py::TestParseSentencesGenerator::test_ends_without_newline tests/test_parser.py::TestParseSentencesGenerator::test_empty tests/test_parser.py::TestParseSentencesGenerator::test_multiple_newlines tests/test_parser.py::TestParseSentencesGenerator::test_simple tests/test_parser.py::TestParseCommentLine::test_parse_comment_line_without_square tests/test_parser.py::TestParseCommentLine::test_parse_comment_line_optional_value tests/test_parser.py::TestParseCommentLine::test_parse_comment_line_optional_value_no_space tests/test_parser.py::TestParseCommentLine::test_parse_comment_line tests/test_parser.py::TestParseCommentLine::test_parse_comment_line_multiple_equals tests/test_parser.py::TestParseCommentLine::test_parse_comment_line_without_equals tests/test_parser.py::TestParseCommentLine::test_parse_spaces_before_square tests/test_parser.py::TestParseCommentLine::test_parse_comment_line_without_space tests/test_parser.py::TestParsePairedListValue::test_parse_empty tests/test_parser.py::TestParsePairedListValue::test_parse_invalid tests/test_parser.py::TestSerialize::test_serialize_tricky_fields tests/test_parser.py::TestSerialize::test_metadata tests/test_parser.py::TestSerialize::test_identity_unicode