diff --git a/polytope_feature/datacube/backends/fdb.py b/polytope_feature/datacube/backends/fdb.py
index d0e20ec8..a45065f7 100644
--- a/polytope_feature/datacube/backends/fdb.py
+++ b/polytope_feature/datacube/backends/fdb.py
@@ -80,10 +80,19 @@ def check_branching_axes(self, request):
                     (upper, lower, idx) = polytope.extents(ax)
                     if "sfc" in polytope.points[idx]:
                         self.fdb_coordinates.pop("levelist", None)
+
+                if ax == "param":
+                    (upper, lower, idx) = polytope.extents(ax)
+                    if "140251" not in polytope.points[idx]:
+                        self.fdb_coordinates.pop("direction", None)
+                        self.fdb_coordinates.pop("frequency", None)
+                    else:
+                        # special param with direction and frequency
+                        if len(polytope.points[idx]) > 1:
+                            raise ValueError(
+                                "Param 251 is part of a special branching of the datacube. Please request it separately."  # noqa: E501
+                            )
         self.fdb_coordinates.pop("quantile", None)
-        # TODO: When do these not appear??
-        self.fdb_coordinates.pop("direction", None)
-        self.fdb_coordinates.pop("frequency", None)
         self.fdb_coordinates.pop("year", None)
         self.fdb_coordinates.pop("month", None)
 
diff --git a/tests/test_wave_spectra_data.py b/tests/test_wave_spectra_data.py
new file mode 100644
index 00000000..6835fee4
--- /dev/null
+++ b/tests/test_wave_spectra_data.py
@@ -0,0 +1,99 @@
+import pandas as pd
+import pytest
+from helper_functions import find_nearest_latlon
+
+from polytope_feature.engine.hullslicer import HullSlicer
+from polytope_feature.polytope import Polytope, Request
+from polytope_feature.shapes import Box, Select
+
+
+class TestWaveData:
+    def setup_method(self, method):
+        self.options = {
+            "axis_config": [
+                {"axis_name": "number", "transformations": [{"name": "type_change", "type": "int"}]},
+                {"axis_name": "step", "transformations": [{"name": "type_change", "type": "int"}]},
+                {
+                    "axis_name": "date",
+                    "transformations": [{"name": "merge", "other_axis": "time", "linkers": ["T", "00"]}],
+                },
+                {
+                    "axis_name": "values",
+                    "transformations": [
+                        {"name": "mapper", "type": "octahedral", "resolution": 1280, "axes": ["latitude", "longitude"]}
+                    ],
+                },
+                {"axis_name": "longitude", "transformations": [{"name": "cyclic", "range": [0, 360]}]},
+                {"axis_name": "latitude", "transformations": [{"name": "reverse", "is_reverse": True}]},
+            ],
+            "pre_path": {"class": "od", "expver": "0001", "type": "fc", "stream": "wave", "date": "20250201"},
+            "compressed_axes_config": [
+                "longitude",
+                "latitude",
+                "levtype",
+                "step",
+                "date",
+                "domain",
+                "expver",
+                "param",
+                "class",
+                "stream",
+                "type",
+                "number",
+            ],
+        }
+        self.slicer = HullSlicer()
+
+    @pytest.mark.fdb
+    def test_healpix_grid(self):
+        import pygribjump as gj
+
+        self.fdb_datacube = gj.GribJump()
+        self.API = Polytope(
+            datacube=self.fdb_datacube,
+            engine=self.slicer,
+            options=self.options,
+        )
+
+        request = Request(
+            Select("step", [1]),
+            Select("date", [pd.Timestamp("20250201T000000")]),
+            Select("domain", ["g"]),
+            Select("expver", ["0001"]),
+            Select("param", ["140251"]),
+            Select("class", ["od"]),
+            Select("stream", ["wave"]),
+            Select("type", ["fc"]),
+            Select("direction", ["1"]),
+            Select("frequency", ["1"]),
+            Box(["latitude", "longitude"], [1, 1], [2, 2]),
+            Select("levtype", ["sfc"]),
+        )
+        result = self.API.retrieve(request)
+        result.pprint()
+        assert len(result.leaves) == 14
+        assert result.leaves[0].result[1].size == 1
+        assert result.leaves[1].result[1].size == 1
+
+        lats = []
+        lons = []
+        eccodes_lats = []
+        tol = 1e-8
+        leaves = result.leaves
+        for i, leaf in enumerate(leaves):
+            cubepath = leaf.flatten()
+            lat = cubepath["latitude"][0]
+            new_lons = cubepath["longitude"]
+            for j, lon in enumerate(new_lons):
+                lats.append(lat)
+                lons.append(lon)
+                nearest_points = find_nearest_latlon("./tests/data/wave_spectra.grib", lat, lon)
+                eccodes_lat = nearest_points[0][0]["lat"]
+                eccodes_lon = nearest_points[0][0]["lon"]
+                assert eccodes_lat - tol <= lat
+                assert lat <= eccodes_lat + tol
+                assert eccodes_lon - tol <= lon
+                assert lon <= eccodes_lon + tol
+                tol = 1e-2
+            eccodes_lats.append(lat)
+        assert len(eccodes_lats) == 14