diff --git a/examples/IOC_data.ipynb b/examples/IOC_data.ipynb
index 678c290..65d096e 100644
--- a/examples/IOC_data.ipynb
+++ b/examples/IOC_data.ipynb
@@ -119,7 +119,7 @@
    },
    "outputs": [],
    "source": [
-    "east_stations[~east_stations.contacts.str.contains(\"NOAA\")]"
+    "east_stations[~east_stations.contacts.str.contains(\"NOAA\", na=False)]"
    ]
   },
   {
@@ -253,7 +253,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "python3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -267,7 +267,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.16"
+   "version": "3.10.9"
   }
  },
  "nbformat": 4,
diff --git a/searvey/coops.py b/searvey/coops.py
index b3034dd..f345a0a 100644
--- a/searvey/coops.py
+++ b/searvey/coops.py
@@ -821,10 +821,9 @@ def coops_stations_within_region(
     """
 
     stations = coops_stations(station_status=station_status)
-    if region:
+    if region is not None:
         return stations[stations.within(region)]
-    else:
-        return stations
+    return stations
 
 
 def coops_stations_within_bounds(
diff --git a/searvey/stations.py b/searvey/stations.py
index faba4f1..1055bc1 100644
--- a/searvey/stations.py
+++ b/searvey/stations.py
@@ -51,6 +51,8 @@ def _get_ioc_stations(
     ioc_gdf = ioc.get_ioc_stations(region=region)
 
     # Normalize IOC
+    # Drop delay `NA'` : https://github.com/oceanmodeling/searvey/issues/91
+    ioc_gdf = ioc_gdf[ioc_gdf.delay != "NA'"]
     # Convert delay to minutes
     ioc_gdf = ioc_gdf.assign(
         delay=pd.concat(