diff --git a/appveyor.yml b/appveyor.yml
index 7a211e88..436c411d 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,42 +1,66 @@
 # version here is only relevant for the AppVeyor CI, no need to adjust
 version: '{build}'
 
+image:
+  - macOS
+  - Ubuntu2004
+
+platform:
+  - x64
+
 environment:
-  global:
-    PYTHON_LOC: "C:\\Miniconda37-x64"
+  # For the unit-tests, disable Numba JIT, otherwise Coverage wont reach the actual Python code
+  NUMBA_DISABLE_JIT: 1
+  # Uncomment following line if web testing breaks our build
+  CATE_DISABLE_WEB_TESTS: 1
+  # geopandas in tests break the build on appveyor (maybe the problem of gdal?)
+  CATE_DISABLE_GEOPANDAS_TESTS: 1
+  CATE_DISABLE_PLOT_TESTS: 1
+  CATE_DISABLE_CLI_UPDATE_TESTS: 1
+
+for:
+-
+  matrix:
+    only:
+      - image: macOS
+  install:
+    - curl -L https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh > miniconda.sh
+    - bash miniconda.sh -b -p $HOME/miniconda
+-
+  matrix:
+    only:
+      - image: Ubuntu2004
+  install:
+    - wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh
+    - bash miniconda.sh -b -p $HOME/miniconda
 
-install:
-  - call %PYTHON_LOC%\Scripts\activate.bat
+build_script:
+  - export PATH="$HOME/miniconda/bin:$PATH"
+  - hash -r
   - conda config --set always_yes yes --set changeps1 no
   - conda config --set channel_priority strict
   - conda update -q conda
   - conda info -a
-  - conda install -c conda-forge -n base mamba
+  - conda init bash
+  - export CONDA_BASE=$(conda info --base)
+  - source $CONDA_BASE/etc/profile.d/conda.sh
+  - conda install -c conda-forge -n base mamba pip
 
-build_script:
-  - call %PYTHON_LOC%\Scripts\activate.bat
   - git clone https://github.com/dcs4cop/xcube.git
   - git clone https://github.com/dcs4cop/xcube-cci.git
   # Install xcube env and xcube
   - cd xcube
   - mamba env create
   - conda activate xcube
-  - python setup.py develop
+  - pip install -e .
   # Install xcube-cci
-  - cd ..\xcube-cci
+  - cd ..
+  - cd xcube-cci
   - mamba install -c conda-forge lxml pydap aiohttp nest-asyncio
-  - python setup.py develop
+  - pip install -e .
   # Install cate-specific packages
   - cd ..
   - mamba install -c conda-forge cartopy
-  - python setup.py develop
+  - pip install -e .
   - conda list
-  # For the unit-tests, disable Numba JIT, otherwise Coverage wont reach the actual Python code
-  - set NUMBA_DISABLE_JIT=1
-  # Uncomment following line if web testing on travis breaks our build
-  - set CATE_DISABLE_WEB_TESTS=1
-  # geopandas in tests break the build on appveyor (maybe the problem of gdal?)
-  - set CATE_DISABLE_GEOPANDAS_TESTS=1
-  - set CATE_DISABLE_PLOT_TESTS=1
-  - set CATE_DISABLE_CLI_UPDATE_TESTS=1
   - pytest -v --cov=cate tests
diff --git a/cate/webapi/geojson.py b/cate/webapi/geojson.py
index e119b5f4..7dfadb94 100644
--- a/cate/webapi/geojson.py
+++ b/cate/webapi/geojson.py
@@ -276,6 +276,18 @@ def write_feature_collection(feature_collection: Union[fiona.Collection, Iterabl
             if num_features_written > 0:
                 io.write(',\n')
                 io.flush()
+            # fiona >=1.9 returns features of type fiona.model.Feature
+            # rather than JSON-serializable dictionaries.
+            if hasattr(feature, '__geo_interface__'):
+                # We fall back on the traditional geo-interface:
+                feature = feature.__geo_interface__
+                # Fiona =1.9.0 adds empty "geometries" field
+                # to any "geometry", we fix this too:
+                geometry = feature.get('geometry')
+                if geometry \
+                        and "geometries" in geometry \
+                        and geometry.get("type") != "GeometryCollection":
+                    del geometry["geometries"]
             if res_id is not None:
                 feature['_resId'] = res_id
             feature['_idx'] = feature_index
diff --git a/tests/ops/test_utility.py b/tests/ops/test_utility.py
index 78119f86..2103b5ad 100644
--- a/tests/ops/test_utility.py
+++ b/tests/ops/test_utility.py
@@ -276,7 +276,7 @@ def test_alloc_memory(self):
         no_op(step_duration=0, num_steps=3, memory_alloc='120M')
         no_op(step_duration=0, num_steps=200, memory_alloc='124B')
         no_op(step_duration=0, num_steps=2, memory_alloc='0.1G')
-        no_op(step_duration=0, num_steps=1, memory_alloc='0.01T')
+        no_op(step_duration=0, num_steps=1, memory_alloc='0.001T')
         with self.assertRaises(ValueError):
             no_op(step_duration=0, num_steps=5, memory_alloc='x')