diff --git a/linkml_runtime/utils/metamodelcore.py b/linkml_runtime/utils/metamodelcore.py
index accdedc8..e4a80eaa 100644
--- a/linkml_runtime/utils/metamodelcore.py
+++ b/linkml_runtime/utils/metamodelcore.py
@@ -172,17 +172,17 @@ def __init__(self, v: str) -> None:
 
     @classmethod
     def ns_ln(cls, v: str) -> Optional[tuple[str, str]]:
-        # See if this is indeed a valid CURIE, ie, it can be split by a colon
+        if not validate_curie(v):
+            return None
+        # assume the presence of a colon and try to split the CURIE
         curie_split = v.split(":", 1)
         if len(curie_split) == 1:
-            # there is no ':' character in the string, ie, it is not a valid CURIE
-            return None
+            # there is no ':' character in the string, it's only a reference
+            return '', v
         else:
             prefix = curie_split[0].lower()
-            if not NCName.is_valid(prefix):
-                return None
             reference = curie_split[1]
-        return prefix, reference
+            return prefix, reference
 
     @classmethod
     def is_valid(cls, v: str) -> bool:
diff --git a/tests/test_utils/test_metamodelcore.py b/tests/test_utils/test_metamodelcore.py
index 63ee247e..df3b03b9 100644
--- a/tests/test_utils/test_metamodelcore.py
+++ b/tests/test_utils/test_metamodelcore.py
@@ -70,11 +70,10 @@ def test_uriorcuries(self):
     def test_curie(self):
         """Test the CURIE type"""
         self.assertEqual("rdf:type", Curie("rdf:type"))
-        with self.assertRaises(ValueError):
-            Curie("type")
-        self.assertFalse(Curie.is_valid("type"))
+        self.assertTrue(Curie.is_valid("type"))
         self.assertEqual(":type", Curie(":type"))
         self.assertTrue(Curie.is_valid(":type"))
+        self.assertTrue(Curie.is_valid("_abc:123"))
         self.assertTrue(Curie.is_valid("WIKIDATA_PROPERTY:P854"))
         self.assertTrue(Curie.is_valid("WIKIDATA.PROPERTY:P854"))
         self.assertTrue(Curie.is_valid("CL:0000001"))
@@ -82,6 +81,7 @@ def test_curie(self):
             Curie("1df:type")
         self.assertFalse(Curie.is_valid("1df:type"))
         self.assertTrue(Curie.is_valid("rdf:17"))
+        self.assertTrue(Curie.is_valid("17"))
         nsm = Namespaces(Graph())
         self.assertEqual(RDF.type, Curie("rdf:type").as_uri(nsm))
         self.assertIsNone(Curie("ex:foo").as_uri(nsm))