diff --git a/CHANGELOG.md b/CHANGELOG.md
index 92b182f..6724340 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+# [v0.5.1] 2025-02-10
+
+- Bump allowed `spacepackets` to v0.28.0
+
 # [v0.5.0] 2025-01-17
 
 ## Added
diff --git a/pyproject.toml b/pyproject.toml
index f56c4ab..14273ec 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,7 @@ build-backend = "setuptools.build_meta"
 name = "cfdp-py"
 description = "Library for high level CCSDS File Delivery Protocol (CFDP) components"
 readme = "README.md"
-version = "0.5.0"
+version = "0.5.1"
 requires-python = ">=3.9"
 license = {text = "Apache-2.0"}
 authors = [
@@ -27,7 +27,7 @@ classifiers = [
   "Topic :: Scientific/Engineering"
 ]
 dependencies = [
-  "spacepackets>=0.26.0, <=0.27",
+  "spacepackets>=0.26.0, <=0.28",
   "crcmod~=1.7",
   "deprecation~=2.1",
 ]
diff --git a/tests/test_src_handler_restricted.py b/tests/test_src_handler_restricted.py
index ff21f3a..77b5330 100644
--- a/tests/test_src_handler_restricted.py
+++ b/tests/test_src_handler_restricted.py
@@ -114,19 +114,23 @@ def test_src_handler_restricted(self):
         self.assertTrue(fsm.states.packets_ready)
         self.assertEqual(fsm.states.num_packets_ready, 1)
         next_pdu = self.source_handler.get_next_packet()
-        self.assertIsInstance(next_pdu.base, MetadataPdu)
+        assert next_pdu is not None
+        self.assertIsInstance(next_pdu.pdu, MetadataPdu)
         fsm = self.source_handler.state_machine()
         self.assertTrue(fsm.states.packets_ready)
-        file_data = self.source_handler.get_next_packet()
-        self.assertIsInstance(file_data.base, FileDataPdu)
+        next_pdu = self.source_handler.get_next_packet()
+        assert next_pdu is not None
+        self.assertIsInstance(next_pdu.pdu, FileDataPdu)
         fsm = self.source_handler.state_machine()
         self.assertTrue(fsm.states.packets_ready)
-        eof_data = self.source_handler.get_next_packet()
-        self.assertIsInstance(eof_data.base, EofPdu)
+        next_pdu = self.source_handler.get_next_packet()
+        assert next_pdu is not None
+        self.assertIsInstance(next_pdu.pdu, EofPdu)
+        assert isinstance(next_pdu.pdu, EofPdu)
         # Send ACK
         pdu_conf = PduConfig(
             direction=Direction.TOWARDS_SENDER,
-            transaction_seq_num=eof_data.base.transaction_seq_num,
+            transaction_seq_num=next_pdu.pdu.transaction_seq_num,
             source_entity_id=self.source_id,
             dest_entity_id=self.dest_id,
             trans_mode=TransmissionMode.ACKNOWLEDGED,
@@ -147,6 +151,7 @@ def test_src_handler_restricted(self):
         fsm = self.source_handler.state_machine(packet=finished)
         self.assertTrue(fsm.states.packets_ready)
         finished_ack = self.source_handler.get_next_packet()
-        self.assertIsInstance(finished_ack.base, AckPdu)
+        assert finished_ack is not None
+        self.assertIsInstance(finished_ack.pdu, AckPdu)
         fsm = self.source_handler.state_machine()
         self.assertEqual(fsm.states.state, CfdpState.IDLE)