diff --git a/common/helpers.py b/common/helpers.py
index 797bb1d1..21cb76f2 100644
--- a/common/helpers.py
+++ b/common/helpers.py
@@ -6,7 +6,7 @@
 from sqlalchemy.exc import IntegrityError
 
 from common.database_helpers import get_icat_db_session
-from common.exceptions import MissingRecordError, BadFilterError
+from common.exceptions import MissingRecordError, BadFilterError, AuthenticationError
 from common.models.db_models import SESSION
 
 
@@ -19,12 +19,15 @@ def requires_session_id(method):
 
     @wraps(method)
     def wrapper_requires_session(*args, **kwargs):
-        session = get_icat_db_session()
-        query = session.query(SESSION).filter(
-            SESSION.ID == get_session_id_from_auth_header()).first()
-        if query is not None:
-            return method(*args, **kwargs)
-        else:
+        try:
+            session = get_icat_db_session()
+            query = session.query(SESSION).filter(
+                SESSION.ID == get_session_id_from_auth_header()).first()
+            if query is not None:
+                return method(*args, **kwargs)
+            else:
+                return "Forbidden", 403
+        except AuthenticationError:
             return "Forbidden", 403
 
     return wrapper_requires_session
@@ -63,9 +66,12 @@ def get_session_id_from_auth_header():
     parser = reqparse.RequestParser()
     parser.add_argument("Authorization", location="headers")
     args = parser.parse_args()
-    if args["Authorization"] is not None:
-        return args["Authorization"]
-    return ""
+    auth_header = args["Authorization"].split(" ") if args["Authorization"] is not None else ""
+    if auth_header == "":
+        return ""
+    if len(auth_header) != 2 or auth_header[0] != "Bearer":
+        raise AuthenticationError()
+    return auth_header[1]
 
 
 def is_valid_json(string):