diff --git a/pyproject.toml b/pyproject.toml
index 364c4cb8..5c781228 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -49,7 +49,6 @@ dependencies = [
     "eccodes>=1.3.0",
     "ecmwf-api-client>=1.6.1",
     "ecmwf-opendata>=0.1.2",
-    "ecmwflibs>=0.6.3",
     "entrypoints",
     "filelock",
     "imageio",
@@ -72,6 +71,7 @@ dependencies = [
 "tensorflow" = ["tensorflow"]
 "zarr" = ["zarr", "s3fs"]
 "interactive" = ["skinnywms", "folium>=0.12.1"]
+"ecmwflibs" = ["ecmwflibs>=0.6.3"]
 
 [project.urls]
 Homepage = "https://github.com/ecmwf/climetlab/"
diff --git a/src/climetlab/datasets/hurricane_database.py b/src/climetlab/datasets/hurricane_database.py
index 63f58d91..f137e4d4 100644
--- a/src/climetlab/datasets/hurricane_database.py
+++ b/src/climetlab/datasets/hurricane_database.py
@@ -98,7 +98,7 @@ def __init__(self, *, bassin="atlantic", url=None):
                 for _ in range(0, int(line[33:36])):
                     line = next(lines)
                     knots = float(line[38:41])
-                    pressure = np.NaN if line[43] == "-" else float(line[43:47])
+                    pressure = np.nan if line[43] == "-" else float(line[43:47])
                     time = "%s-%s-%sZ%s:%s" % (
                         line[0:4],
                         line[4:6],