diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d0d15ef..112ddfc 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -31,21 +31,27 @@ jobs:
       with:
         python-version: ${{ matrix.python_version }}
 
-    - name: Prepare environment
+    - name: Prepare environment (non-Windows systems)
+      if: ${{ matrix.os != 'windows-2019' }}
       run: |
         pip install --upgrade pip pipenv
 
+    - name: Prepare environment (Windows)
+      if: ${{ matrix.os == 'windows-2019' }}
+      run: |
+        python -mpip install --upgrade pip pipenv
+
     - name: Install dependencies (all systems)
       run: |
         pipenv lock --pre
         pipenv sync --dev
         pipenv install --dev
 
-    - name: Install dependencies (Windows-specific)
+    - name: Install dependencies (Windows)
       if: ${{ matrix.os == 'windows-2019' }}
       run: |
         pipenv lock --dev -r > requirements.txt
-        pip install -r requirements.txt
+        python -mpip install -r requirements.txt
 
     - name: Run legacy tests
       run: |
@@ -75,21 +81,27 @@ jobs:
       with:
         python-version: ${{ matrix.python_version }}
 
-    - name: Prepare environment
+    - name: Prepare environment (non-Windows systems)
+      if: ${{ matrix.os != 'windows-2019' }}
       run: |
         pip install --upgrade pip pipenv
 
+    - name: Prepare environment (Windows)
+      if: ${{ matrix.os == 'windows-2019' }}
+      run: |
+        python -mpip install --upgrade pip pipenv
+
     - name: Install dependencies (all systems)
       run: |
         pipenv lock --pre
         pipenv sync --dev
         pipenv install --dev
 
-    - name: Install dependencies (Windows-specific)
+    - name: Install dependencies (Windows)
       if: ${{ matrix.os == 'windows-2019' }}
       run: |
         pipenv lock -r > requirements.txt
-        pip install -r requirements.txt
+        python -mpip install -r requirements.txt
 
     - name: Run doc tests (with coverage)
       if: ${{ matrix.os == 'ubuntu-20.04' && matrix.python_version == '3.9' }}
diff --git a/kosmorrolib/model.py b/kosmorrolib/model.py
index 42db7a9..1f4a362 100644
--- a/kosmorrolib/model.py
+++ b/kosmorrolib/model.py
@@ -114,9 +114,15 @@ class Object(Serializable):
         )
 
     def serialize(self) -> dict:
+        """Serialize the given object
+
+        >>> planet = Planet(ObjectIdentifier.MARS, "MARS")
+        >>> planet.serialize()
+        {'identifier': 'MARS', 'type': 'PLANET', 'radius': None}
+        """
         return {
             "identifier": self.identifier.name,
-            "type": self.get_type(),
+            "type": self.get_type().name,
             "radius": self.radius,
         }