diff --git a/src/geoapis/vector.py b/src/geoapis/vector.py
index 76ac87d..d99eb42 100644
--- a/src/geoapis/vector.py
+++ b/src/geoapis/vector.py
@@ -72,10 +72,21 @@ def __init__(
     def _set_up(self):
         """Ensure the bouding_polygon and CRS are in agreement."""
 
+        error_message = "Either the crs or the bounding_polygon with a CRS mus be specified."
+        if self.crs is None and self.bounding_polygon is None:
+            logging.error(error_message)
+            raise ValueError(error_message)
+
         # Set the crs from the bounding_polygon if it's not been set
-        if self.crs is None and self.bounding_polygon is not None:
-            self.crs = self.bounding_polygon.crs.to_epsg()
-        # Set the bounding_polygon crs from the crs if they differ
+        if self.bounding_polygon is not None:
+            if self.crs is None and self.bounding_polygon.crs is not None:
+                self.crs = self.bounding_polygon.crs.to_epsg()
+            elif self.crs is not None and self.bounding_polygon.crs is None:
+                self.bounding_polygon.set_crs(self.crs, inplace=True)
+            elif self.crs is None and self.bounding_polygon.crs is None:
+                logging.error(error_message)
+                raise ValueError(error_message)
+        # Convert the bounding_polygon crs from the crs if they differ
         if (
             self.bounding_polygon is not None
             and self.crs != self.bounding_polygon.crs.to_epsg()