diff --git a/CHANGELOG.md b/CHANGELOG.md
index c3fb2c6e..d473eae7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Change Log
 
+## Unreleased
+
+- Ensures `GridMetrics` are sent via `msgpack` the same as `Metrics`.
+
 ## [v2.2.2](https://github.com/simvue-io/client/releases/tag/v2.2.2) - 2025-10-14
 
 - Enforced use of UTC for all datetime recording.
diff --git a/simvue/api/objects/grids.py b/simvue/api/objects/grids.py
index 42b50610..4f063ba8 100644
--- a/simvue/api/objects/grids.py
+++ b/simvue/api/objects/grids.py
@@ -258,6 +258,9 @@ def __init__(
         self._run_id = self._staging.get("run")
         self._is_set = True
 
+    def _post_single(self, **kwargs) -> dict[str, typing.Any]:
+        return super()._post_single(is_json=False, **kwargs)
+
     @staticmethod
     def run_grids_endpoint(run: str | None = None) -> URL:
         """Returns the URL for grids for a specific run."""