diff --git a/json/bin/jsonschema_suite b/json/bin/jsonschema_suite
index 9fee8d7ba..c83e7cb2c 100755
--- a/json/bin/jsonschema_suite
+++ b/json/bin/jsonschema_suite
@@ -14,9 +14,11 @@ import warnings
 try:
     import jsonschema.validators
 except ImportError:
-    jsonschema = None
+    jsonschema = Unresolvable = None
     VALIDATORS = {}
 else:
+    from referencing.exceptions import Unresolvable
+
     VALIDATORS = {
         "draft3": jsonschema.validators.Draft3Validator,
         "draft4": jsonschema.validators.Draft4Validator,
@@ -587,7 +589,7 @@ class SanityTests(unittest.TestCase):
                 with self.subTest(case=case, version=version.name):
                     try:
                         Validator(case["schema"]).is_valid(12)
-                    except jsonschema.exceptions.RefResolutionError:
+                    except Unresolvable:
                         pass
 
     @unittest.skipIf(jsonschema is None, "Validation library not present!")
@@ -615,9 +617,6 @@ class SanityTests(unittest.TestCase):
             with self.subTest(path=path):
                 try:
                     validator.validate(cases)
-                except jsonschema.exceptions.RefResolutionError:
-                    # python-jsonschema/jsonschema#884
-                    pass
                 except jsonschema.ValidationError as error:
                     self.fail(str(error))
 
diff --git a/json/tests/draft-next/optional/format/hostname.json b/json/tests/draft-next/optional/format/hostname.json
index 967848653..bfb306363 100644
--- a/json/tests/draft-next/optional/format/hostname.json
+++ b/json/tests/draft-next/optional/format/hostname.json
@@ -95,6 +95,31 @@
                 "description": "exceeds maximum label length",
                 "data": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl.com",
                 "valid": false
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label starting with digit",
+                "data": "1host",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft-next/optional/format/idn-hostname.json b/json/tests/draft-next/optional/format/idn-hostname.json
index ee2e792fa..109bf73c9 100644
--- a/json/tests/draft-next/optional/format/idn-hostname.json
+++ b/json/tests/draft-next/optional/format/idn-hostname.json
@@ -301,6 +301,31 @@
                 "comment": "https://tools.ietf.org/html/rfc5891#section-4.2.3.3 https://tools.ietf.org/html/rfc5892#appendix-A.1 https://www.w3.org/TR/alreq/#h_disjoining_enforcement",
                 "data": "\u0628\u064a\u200c\u0628\u064a",
                 "valid": true
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label starting with digit",
+                "data": "1host",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft2019-09/optional/format/hostname.json b/json/tests/draft2019-09/optional/format/hostname.json
index eac8cac6f..f3b7181c8 100644
--- a/json/tests/draft2019-09/optional/format/hostname.json
+++ b/json/tests/draft2019-09/optional/format/hostname.json
@@ -95,6 +95,31 @@
                 "description": "exceeds maximum label length",
                 "data": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl.com",
                 "valid": false
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label starting with digit",
+                "data": "1host",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft2019-09/optional/format/idn-hostname.json b/json/tests/draft2019-09/optional/format/idn-hostname.json
index 72f179751..072a6b08e 100644
--- a/json/tests/draft2019-09/optional/format/idn-hostname.json
+++ b/json/tests/draft2019-09/optional/format/idn-hostname.json
@@ -301,6 +301,31 @@
                 "comment": "https://tools.ietf.org/html/rfc5891#section-4.2.3.3 https://tools.ietf.org/html/rfc5892#appendix-A.1 https://www.w3.org/TR/alreq/#h_disjoining_enforcement",
                 "data": "\u0628\u064a\u200c\u0628\u064a",
                 "valid": true
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label starting with digit",
+                "data": "1host",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft2020-12/optional/format/hostname.json b/json/tests/draft2020-12/optional/format/hostname.json
index c8db9770e..41418dd4a 100644
--- a/json/tests/draft2020-12/optional/format/hostname.json
+++ b/json/tests/draft2020-12/optional/format/hostname.json
@@ -95,6 +95,31 @@
                 "description": "exceeds maximum label length",
                 "data": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl.com",
                 "valid": false
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label starting with digit",
+                "data": "1host",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft2020-12/optional/format/idn-hostname.json b/json/tests/draft2020-12/optional/format/idn-hostname.json
index 5549c0550..bc7d92f66 100644
--- a/json/tests/draft2020-12/optional/format/idn-hostname.json
+++ b/json/tests/draft2020-12/optional/format/idn-hostname.json
@@ -301,6 +301,31 @@
                 "comment": "https://tools.ietf.org/html/rfc5891#section-4.2.3.3 https://tools.ietf.org/html/rfc5892#appendix-A.1 https://www.w3.org/TR/alreq/#h_disjoining_enforcement",
                 "data": "\u0628\u064a\u200c\u0628\u064a",
                 "valid": true
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label starting with digit",
+                "data": "1host",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft4/optional/format/hostname.json b/json/tests/draft4/optional/format/hostname.json
index 8a67fda88..a8ecd194f 100644
--- a/json/tests/draft4/optional/format/hostname.json
+++ b/json/tests/draft4/optional/format/hostname.json
@@ -92,6 +92,26 @@
                 "description": "exceeds maximum label length",
                 "data": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl.com",
                 "valid": false
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft6/optional/format/hostname.json b/json/tests/draft6/optional/format/hostname.json
index 8a67fda88..a8ecd194f 100644
--- a/json/tests/draft6/optional/format/hostname.json
+++ b/json/tests/draft6/optional/format/hostname.json
@@ -92,6 +92,26 @@
                 "description": "exceeds maximum label length",
                 "data": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl.com",
                 "valid": false
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft7/optional/format/hostname.json b/json/tests/draft7/optional/format/hostname.json
index 8a67fda88..a8ecd194f 100644
--- a/json/tests/draft7/optional/format/hostname.json
+++ b/json/tests/draft7/optional/format/hostname.json
@@ -92,6 +92,26 @@
                 "description": "exceeds maximum label length",
                 "data": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl.com",
                 "valid": false
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tests/draft7/optional/format/idn-hostname.json b/json/tests/draft7/optional/format/idn-hostname.json
index 6c8f86a3a..dc47f7b5c 100644
--- a/json/tests/draft7/optional/format/idn-hostname.json
+++ b/json/tests/draft7/optional/format/idn-hostname.json
@@ -298,6 +298,26 @@
                 "comment": "https://tools.ietf.org/html/rfc5891#section-4.2.3.3 https://tools.ietf.org/html/rfc5892#appendix-A.1 https://www.w3.org/TR/alreq/#h_disjoining_enforcement",
                 "data": "\u0628\u064a\u200c\u0628\u064a",
                 "valid": true
+            },
+            {
+                "description": "single label",
+                "data": "hostname",
+                "valid": true
+            },
+            {
+                "description": "single label with hyphen",
+                "data": "host-name",
+                "valid": true
+            },
+            {
+                "description": "single label with digits",
+                "data": "h0stn4me",
+                "valid": true
+            },
+            {
+                "description": "single label ending with digit",
+                "data": "hostnam3",
+                "valid": true
             }
         ]
     }
diff --git a/json/tox.ini b/json/tox.ini
index dcc0dce6d..a5ded970e 100644
--- a/json/tox.ini
+++ b/json/tox.ini
@@ -5,5 +5,5 @@ skipsdist = True
 
 [testenv:sanity]
 # used just for validating the structure of the test case files themselves
-deps = jsonschema==4.18.0a4
+deps = jsonschema==4.19.0
 commands = {envpython} bin/jsonschema_suite check