diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4fda18f5..d5c8a7a6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -34,9 +34,21 @@ jobs:
           - os: ubuntu-latest
             python-version: "3.8"
 
+  test-minreqs:
+    uses: pyapp-kit/workflows/.github/workflows/test-pyrepo.yml@main
+    with:
+      os: ubuntu-latest
+      python-version: ${{ matrix.python-version }}
+      pip-install-min-reqs: true
+      coverage-upload: artifact
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.9", "3.12"]
+
   upload_coverage:
     if: always()
-    needs: [test]
+    needs: [test, test-minreqs]
     uses: pyapp-kit/workflows/.github/workflows/upload-coverage.yml@v2
     secrets:
       CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
diff --git a/pyproject.toml b/pyproject.toml
index 7efb8c2e..75df06c9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,7 +32,7 @@ classifiers = [
     "Typing :: Typed",
 ]
 dynamic = ["version"]
-dependencies = ["pydantic >=2,!=2.4.1", "numpy", "typing-extensions"]
+dependencies = ["pydantic >=2.6", "numpy", "typing-extensions"]
 
 # extras
 # https://peps.python.org/pep-0621/#dependencies-optional-dependencies
diff --git a/src/useq/_mda_sequence.py b/src/useq/_mda_sequence.py
index 726966f7..dc9e2eeb 100644
--- a/src/useq/_mda_sequence.py
+++ b/src/useq/_mda_sequence.py
@@ -184,7 +184,9 @@ class MDASequence(UseqModel):
     stage_positions: Union[WellPlatePlan, Tuple[Position, ...]] = Field(
         default_factory=tuple
     )
-    grid_plan: Optional[MultiPointPlan] = None
+    grid_plan: Optional[MultiPointPlan] = Field(
+        default=None, union_mode="left_to_right"
+    )
     channels: Tuple[Channel, ...] = Field(default_factory=tuple)
     time_plan: Optional[AnyTimePlan] = None
     z_plan: Optional[AnyZPlan] = None