diff --git a/.github/workflows/ci_tests.yml b/.github/workflows/ci_tests.yml
index dbc1c57..ec9080b 100644
--- a/.github/workflows/ci_tests.yml
+++ b/.github/workflows/ci_tests.yml
@@ -32,3 +32,15 @@ jobs:
     - name: Test with tox
       run: |
         tox
+
+  minimal-dependencies:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Create virtual env
+        run: python3 -m venv venv --upgrade-deps
+      - name: Install pyaro
+        run: source venv/bin/activate && pip install ./
+      - name: Try importing pyaro
+        run: source venv/bin/activate && python -c "import pyaro; print(pyaro.__version__)"
+    
diff --git a/src/pyaro/timeseries/Filter.py b/src/pyaro/timeseries/Filter.py
index 3c92226..1a3fd38 100644
--- a/src/pyaro/timeseries/Filter.py
+++ b/src/pyaro/timeseries/Filter.py
@@ -1227,11 +1227,11 @@ def __init__(
         upper: float | None = None,
     ):
         if "cf_units" not in sys.modules:
-            raise ModuleNotFoundError(
+            logger.info(
                 "valleyfloor_relaltitude filter is missing required dependency 'cf-units'. Please install to use this filter."
             )
         if "xarray" not in sys.modules:
-            raise ModuleNotFoundError(
+            logger.info(
                 "valleyfloor_relaltitude filter is missing required dependency 'xarray'. Please install to use this filter."
             )
 
@@ -1254,8 +1254,16 @@ def name(self):
         return "valleyfloor_relaltitude"
 
     def filter_stations(self, stations: dict[str, Station]) -> dict[str, Station]:
-        filtered_stations = {}
+        if "cf_units" not in sys.modules:
+            raise ModuleNotFoundError(
+                "valleyfloor_relaltitude filter is missing required dependency 'cf-units'. Please install to use this filter."
+            )
+        if "xarray" not in sys.modules:
+            raise ModuleNotFoundError(
+                "valleyfloor_relaltitude filter is missing required dependency 'xarray'. Please install to use this filter."
+            )
 
+        filtered_stations = {}
         with xr.open_dataset(self._topo_file) as topo:
             for k, v in stations.items():
                 lat = v.latitude
@@ -1285,7 +1293,7 @@ def _calculate_relative_altitude(
         *,
         radius: float,
         altitude: float,
-        topo: xr.Dataset,
+        topo: "xr.Dataset",
     ):
         """Calculates relative altitude