diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2e96b2fb6a..cbc7f5572d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,14 +25,11 @@ jobs:
       matrix:
         os: [ubuntu] #, mac, windows] # TODO v4: Re-enable windows and mac
         test-subfolder: ["/"]
-        python-version: ["3.13"]
+        python-version: ["3.12"]
         include:
           - os: ubuntu
             python-version: "3.11"
             test-subfolder: "/"
-          - os: ubuntu
-            python-version: "3.12"
-            test-subfolder: "/"
           - os: ubuntu
             python-version: "3.12"
             test-subfolder: "/v4"
@@ -52,7 +49,6 @@ jobs:
         uses: codecov/codecov-action@v5.3.1
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
-        if: matrix.python-version == '3.13'
         with:
           flags: unit-tests
       - name: Upload test results
@@ -68,7 +64,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu] #, mac, windows] # TODO v4: Re-enable windows and mac
-        python-version: ["3.13"]
+        python-version: ["3.12"]
         include:
           - os: ubuntu
             python-version: "3.11"
diff --git a/environment.yml b/environment.yml
index e3c9d5c74e..021a29d751 100644
--- a/environment.yml
+++ b/environment.yml
@@ -2,7 +2,7 @@ name: parcels
 channels:
   - conda-forge
 dependencies: #! Keep in sync with [tool.pixi.dependencies] in pyproject.toml
-  - python>=3.11
+  - python>=3.11, <3.13
   - ffmpeg>=3.2.3
   - jupyter
   - matplotlib-base>=2.0.2
diff --git a/parcels/field.py b/parcels/field.py
index 8063a85afc..d739b3f86c 100644
--- a/parcels/field.py
+++ b/parcels/field.py
@@ -142,7 +142,7 @@ def __init__(
         self,
         name: str,
         data: xr.DataArray | ux.UxDataArray,
-        grid: ux.UxGrid | None = None,  # TODO Nick : Once parcels.Grid class is added, allow for it to be passed here
+        grid: ux.Grid | None = None,  # TODO Nick : Once parcels.Grid class is added, allow for it to be passed here
         mesh_type: Mesh = "flat",
         interp_method: Callable | None = None,
         allow_time_extrapolation: bool | None = None,
diff --git a/parcels/fieldset.py b/parcels/fieldset.py
index 9c8ee9315f..c0f5842258 100644
--- a/parcels/fieldset.py
+++ b/parcels/fieldset.py
@@ -139,7 +139,6 @@ def add_field(self, field: Field, name: str | None = None):
             raise RuntimeError(f"FieldSet already has a Field with name '{name}'")
         else:
             setattr(self, name, field)
-            self._gridset_size += 1
             self._fieldnames.append(name)
 
     def add_constant_field(self, name: str, value, mesh: Mesh = "flat"):
diff --git a/pyproject.toml b/pyproject.toml
index 361d8a8d36..fddc2387db 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -8,7 +8,7 @@ description = "Framework for Lagrangian tracking of virtual ocean particles in t
 readme = "README.md"
 dynamic = ["version"]
 authors = [{name = "oceanparcels.org team"}]
-requires-python = ">=3.11"
+requires-python = ">=3.11,<3.13"
 license = {file = "LICENSE.md"}
 classifiers = [
   "License :: OSI Approved :: MIT License",