doc/news.rst           |  3 +++
 pyderasn.py            |  2 +-
 tests/test_pyderasn.py | 16 +++++++++++-----

diff --git a/doc/news.rst b/doc/news.rst
index ecd06c605683581a1718159c61aafd4dfa0c9feabb61cc990c5c763f40a51873..873bfff42a32af65a0b5c4611cd73da558a4ef238c9f25257c43435889a4ea31 100644
--- a/doc/news.rst
+++ b/doc/news.rst
@@ -5,6 +5,9 @@ .. _release3.10:
 
 3.10
 ----
+* Fix long-standing bug with explicitly tagged objects inside the
+  Choice. If Choice had explicitly tagged value, then its ``.tlvlen``
+  reports the size without taking value's explicit tag in advance.
 * Add ``.fulllen`` and ``.fulloffset`` properties for all objects
 
 .. _release3.9:
diff --git a/pyderasn.py b/pyderasn.py
index 08e66a7071f9788f049c00c22cd57284afc0bedf7a397be838da7e6d2dfd943d..c98c35301d69f8d7db5b3b8fb9bca80b290dae7fd1222c270f1357133a76950a 100755
--- a/pyderasn.py
+++ b/pyderasn.py
@@ -3896,7 +3896,7 @@             schema=self.specs,
             expl=self._expl,
             default=self.default,
             optional=self.optional,
-            _decoded=(offset, 0, value.tlvlen),
+            _decoded=(offset, 0, value.fulllen),
         )
         obj._value = (choice, value)
         return obj, tail
diff --git a/tests/test_pyderasn.py b/tests/test_pyderasn.py
index 6ae434c4b491cc8587bbeb563c5548d7e697094fae876090c43ceea8d157543c..1e732f4ce948462b1d27b89df9437c4374bb13ece827f0d240a2b14b57ccc477 100644
--- a/tests/test_pyderasn.py
+++ b/tests/test_pyderasn.py
@@ -3928,12 +3928,18 @@ @composite
 def choice_values_strategy(draw, value_required=False, schema=None, do_expl=False):
     if schema is None:
         names = list(draw(sets(text_letters(), min_size=1, max_size=5)))
-        tags = [tag_encode(tag) for tag in draw(sets(
-            integers(min_value=0),
+        tags = [{tag_type: tag_value} for tag_type, tag_value in draw(sets(
+            one_of(
+                tuples(just("impl"), integers(min_value=0).map(tag_encode)),
+                tuples(just("expl"), integers(min_value=0).map(tag_ctxp)),
+            ),
             min_size=len(names),
             max_size=len(names),
         ))]
-        schema = [(name, Integer(impl=tag)) for name, tag in zip(names, tags)]
+        schema = [
+            (name, Integer(**tag_kwargs))
+            for name, tag_kwargs in zip(names, tags)
+        ]
     value = None
     if value_required or draw(booleans()):
         value = draw(tuples(
@@ -4175,8 +4181,8 @@         )
         self.assertEqual(obj_decoded.expl_offset, offset)
         self.assertSequenceEqual(
             obj_expled_encoded[
-                obj_decoded.value.offset - offset:
-                obj_decoded.value.offset + obj_decoded.value.tlvlen - offset
+                obj_decoded.value.fulloffset - offset:
+                obj_decoded.value.fulloffset + obj_decoded.value.fulllen - offset
             ],
             obj_encoded,
         )