diff --git a/CHANGELOG.yaml b/CHANGELOG.yaml
index 44c09a7..723d671 100644
--- a/CHANGELOG.yaml
+++ b/CHANGELOG.yaml
@@ -42,6 +42,7 @@ Unreleased:
   added: []
   changed: []
   deprecated: []
-  fixed: []
+  fixed:
+  - better range check for unallocated ASNs
   removed: []
   security: []
diff --git a/rdap/objects.py b/rdap/objects.py
index 205934f..ed497db 100644
--- a/rdap/objects.py
+++ b/rdap/objects.py
@@ -1,4 +1,4 @@
-from builtins import object
+from rdap.exceptions import RdapNotFoundError
 
 
 class RdapObject(object):
@@ -139,6 +139,13 @@ class RdapAsn(RdapObject):
     """
 
     def __init__(self, data, rdapc=None):
+        # check for ASN range, meaning it's delegated and unallocated
+        if data:
+            start = data.get("startAutnum", None)
+            end = data.get("endAutnum", None)
+            if start and end and start != end:
+                raise RdapNotFoundError("AS{} returned a block, so it is not allocated".format(start))
+
         super().__init__(data, rdapc)