diff --git a/.github/workflows/python_actions.yml b/.github/workflows/python_actions.yml
index b371619e..173be2e9 100644
--- a/.github/workflows/python_actions.yml
+++ b/.github/workflows/python_actions.yml
@@ -20,7 +20,7 @@ on: [push]
 
 jobs:
   call:
-    uses: SpiNNakerManchester/SupportScripts/.github/workflows/python_checks.yml@main
+    uses: SpiNNakerManchester/SupportScripts/.github/workflows/python_checks.yml@mypy2
     with:
       dependencies: SpiNNUtils SpiNNMachine SpiNNMan PACMAN spalloc SpiNNFrontEndCommon TestBase
       ubuntu-packages: graphviz
diff --git a/gfe_examples/template/template_vertex.py b/gfe_examples/template/template_vertex.py
index 491cff9e..bfaf6bd7 100644
--- a/gfe_examples/template/template_vertex.py
+++ b/gfe_examples/template/template_vertex.py
@@ -120,7 +120,7 @@ def _write_app_memory_regions(self, spec: DataSpecificationGenerator,
         spec.write_value(int(key is not None))
         spec.write_value(0 if key is None else key)
 
-    def read(self) -> bytes:
+    def read(self) -> memoryview:
         """
         Get the recorded data.
 
diff --git a/gfe_integration_tests/test_extra_monitor/test_extra_monitor.py b/gfe_integration_tests/test_extra_monitor/test_extra_monitor.py
index 95c040d9..3d6d1dd8 100644
--- a/gfe_integration_tests/test_extra_monitor/test_extra_monitor.py
+++ b/gfe_integration_tests/test_extra_monitor/test_extra_monitor.py
@@ -42,7 +42,7 @@ def get_data_region_address(placement: Placement, region: DataRegions) -> int:
     return transceiver.read_word(placement.x, placement.y, address_location)
 
 
-def check_data(data: bytes) -> None:
+def check_data(data: bytearray) -> None:
     # check data is correct here
     ints = n_word_struct(len(data) // 4).unpack(data)
     start_value = 0
@@ -57,7 +57,7 @@ def check_data(data: bytes) -> None:
 
 def _do_transfer(gatherer: DataSpeedUpPacketGatherMachineVertex,
                  receiver_placement: Placement, writer_placement: Placement,
-                 writer_vertex: SDRAMWriter) -> bytes:
+                 writer_vertex: SDRAMWriter) -> bytearray:
     with StreamingContextManager(FecDataView.iterate_gathers()):
         extra_monitor = receiver_placement.vertex
         assert isinstance(extra_monitor, ExtraMonitorSupportMachineVertex)
diff --git a/spinnaker_graph_front_end/utilities/simulator_vertex.py b/spinnaker_graph_front_end/utilities/simulator_vertex.py
index d971c836..827f189d 100644
--- a/spinnaker_graph_front_end/utilities/simulator_vertex.py
+++ b/spinnaker_graph_front_end/utilities/simulator_vertex.py
@@ -97,7 +97,7 @@ def placement(self) -> Placement:
         return FecDataView.get_placement_of_vertex(self)
 
     def get_recording_channel_data(
-            self, recording_id: int) -> Tuple[bytes, bool]:
+            self, recording_id: int) -> Tuple[memoryview, bool]:
         """
         Get the data from a recording channel. The simulation must have
         :py:func:`spinnaker_graph_front_end.run` before this will work,