diff --git a/osm_fieldwork/OdkCentral.py b/osm_fieldwork/OdkCentral.py
index 39bf5ca72..0c8341d4e 100755
--- a/osm_fieldwork/OdkCentral.py
+++ b/osm_fieldwork/OdkCentral.py
@@ -185,18 +185,24 @@ def authenticate(
         self.session.headers.update({"accept": "odkcentral"})
 
         # Get a session token
-        response = self.session.post(
-            f"{self.base}sessions",
-            json={
-                "email": self.user,
-                "password": self.passwd,
-            },
-        )
+        try:
+            response = self.session.post(
+                f"{self.base}sessions",
+                json={
+                    "email": self.user,
+                    "password": self.passwd,
+                },
+            )
+        except requests.exceptions.ConnectionError as request_error:
+            # URL does not exist
+            raise ConnectionError("Failed to connect to Central. Is the URL valid?") from request_error
+
         if response.status_code == 401:
             # Unauthorized, invalid credentials
-            raise ValueError("ODK credentials are invalid, or may have been updated. Please update them.")
+            raise ConnectionError("ODK credentials are invalid, or may have changed. Please update them.") from None
         elif not response.ok:
-            response.raise_for_status()  # Handle other errors
+            # Handle other errors
+            response.raise_for_status()
 
         self.session.headers.update({"Authorization": f"Bearer {response.json().get('token')}"})
 
diff --git a/osm_fieldwork/OdkCentralAsync.py b/osm_fieldwork/OdkCentralAsync.py
index e7c6c0ed2..8290305ae 100755
--- a/osm_fieldwork/OdkCentralAsync.py
+++ b/osm_fieldwork/OdkCentralAsync.py
@@ -90,9 +90,18 @@ async def __aexit__(self, exc_type, exc_value, traceback):
 
     async def authenticate(self):
         """Authenticate to an ODK Central server."""
-        async with self.session.post(f"{self.base}sessions", json={"email": self.user, "password": self.passwd}) as response:
-            token = (await response.json())["token"]
-            self.session.headers.update({"Authorization": f"Bearer {token}"})
+        try:
+            async with self.session.post(f"{self.base}sessions", json={"email": self.user, "password": self.passwd}) as response:
+                token = (await response.json())["token"]
+                self.session.headers.update({"Authorization": f"Bearer {token}"})
+        except aiohttp.ClientConnectorError as request_error:
+            await self.session.close()
+            raise ConnectionError("Failed to connect to Central. Is the URL valid?") from request_error
+        except aiohttp.ClientResponseError as response_error:
+            await self.session.close()
+            if response_error.status == 401:
+                raise ConnectionError("ODK credentials are invalid, or may have changed. Please update them.") from response_error
+            raise response_error
 
 
 class OdkProject(OdkCentral):