diff --git a/test/jsonschema/frame/draft2/requires_holding_a_schema.json b/test/jsonschema/frame/draft2/requires_holding_a_schema.json
new file mode 100644
index 0000000000..e23c550b0e
--- /dev/null
+++ b/test/jsonschema/frame/draft2/requires_holding_a_schema.json
@@ -0,0 +1,159 @@
+{
+  "schema": {
+    "$schema": "http://json-schema.org/draft-02/schema#",
+    "properties": {
+      "one": {
+        "requires": {
+          "type": "string"
+        }
+      }
+    }
+  },
+  "root": {
+    "mode": "root",
+    "locations": {
+      "static": {
+        "": {
+          "parent": null,
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "",
+          "relativePointer": "",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        }
+      },
+      "dynamic": {}
+    },
+    "references": []
+  },
+  "pointers": {
+    "mode": "pointers",
+    "locations": {
+      "static": {
+        "": {
+          "parent": null,
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "",
+          "relativePointer": "",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        },
+        "#/$schema": {
+          "parent": "",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/$schema",
+          "relativePointer": "/$schema",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        },
+        "#/properties": {
+          "parent": "",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/properties",
+          "relativePointer": "/properties",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        },
+        "#/properties/one": {
+          "parent": "",
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "/properties/one",
+          "relativePointer": "/properties/one",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        },
+        "#/properties/one/requires": {
+          "parent": "/properties/one",
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "/properties/one/requires",
+          "relativePointer": "/properties/one/requires",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        },
+        "#/properties/one/requires/type": {
+          "parent": "/properties/one/requires",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/properties/one/requires/type",
+          "relativePointer": "/properties/one/requires/type",
+          "dialect": "http://json-schema.org/draft-02/schema#",
+          "baseDialect": "http://json-schema.org/draft-02/hyper-schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-02/schema#": true
+          }
+        }
+      },
+      "dynamic": {}
+    },
+    "references": [
+      {
+        "type": "static",
+        "origin": "/$schema",
+        "original": "http://json-schema.org/draft-02/schema#",
+        "destination": "http://json-schema.org/draft-02/schema",
+        "base": "http://json-schema.org/draft-02/schema",
+        "fragment": null
+      }
+    ]
+  },
+  "standalone": true
+}
diff --git a/test/jsonschema/frame/draft3/disallow_holding_a_schema.json b/test/jsonschema/frame/draft3/disallow_holding_a_schema.json
new file mode 100644
index 0000000000..480464f799
--- /dev/null
+++ b/test/jsonschema/frame/draft3/disallow_holding_a_schema.json
@@ -0,0 +1,158 @@
+{
+  "schema": {
+    "$schema": "http://json-schema.org/draft-03/schema#",
+    "disallow": [
+      {
+        "type": "string"
+      },
+      "null"
+    ]
+  },
+  "root": {
+    "mode": "root",
+    "locations": {
+      "static": {
+        "": {
+          "parent": null,
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "",
+          "relativePointer": "",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        }
+      },
+      "dynamic": {}
+    },
+    "references": []
+  },
+  "pointers": {
+    "mode": "pointers",
+    "locations": {
+      "static": {
+        "": {
+          "parent": null,
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "",
+          "relativePointer": "",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        },
+        "#/$schema": {
+          "parent": "",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/$schema",
+          "relativePointer": "/$schema",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        },
+        "#/disallow": {
+          "parent": "",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/disallow",
+          "relativePointer": "/disallow",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        },
+        "#/disallow/0": {
+          "parent": "",
+          "type": "subschema",
+          "root": null,
+          "base": "",
+          "pointer": "/disallow/0",
+          "relativePointer": "/disallow/0",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        },
+        "#/disallow/0/type": {
+          "parent": "/disallow/0",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/disallow/0/type",
+          "relativePointer": "/disallow/0/type",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        },
+        "#/disallow/1": {
+          "parent": "",
+          "type": "pointer",
+          "root": null,
+          "base": "",
+          "pointer": "/disallow/1",
+          "relativePointer": "/disallow/1",
+          "dialect": "http://json-schema.org/draft-03/schema#",
+          "baseDialect": "http://json-schema.org/draft-03/schema#",
+          "propertyName": false,
+          "orphan": false,
+          "hasReferencesTo": false,
+          "hasReferencesThrough": false,
+          "vocabularies": {
+            "http://json-schema.org/draft-03/schema#": true
+          }
+        }
+      },
+      "dynamic": {}
+    },
+    "references": [
+      {
+        "type": "static",
+        "origin": "/$schema",
+        "original": "http://json-schema.org/draft-03/schema#",
+        "destination": "http://json-schema.org/draft-03/schema",
+        "base": "http://json-schema.org/draft-03/schema",
+        "fragment": null
+      }
+    ]
+  },
+  "standalone": true
+}
diff --git a/test/jsonschema/jsonschema_frame_error_test.cc b/test/jsonschema/jsonschema_frame_error_test.cc
index a52be9ae89..4fd3fd889b 100644
--- a/test/jsonschema/jsonschema_frame_error_test.cc
+++ b/test/jsonschema/jsonschema_frame_error_test.cc
@@ -2639,3 +2639,26 @@ TEST(draft7_root_id_fragment_invalid_leading_digit_root_mode) {
     FAIL();
   }
 }
+
+TEST(identifier_that_is_not_a_valid_uri) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "$id": "https://example.com/schema",
+    "$defs": {
+      "inner": { "$id": "//[::44.1" }
+    }
+  })JSON");
+
+  try {
+    [[maybe_unused]] const sourcemeta::core::SchemaFrame frame{
+        sourcemeta::core::SchemaFrame::Mode::References, document,
+        sourcemeta::core::schema_walker, sourcemeta::core::schema_resolver};
+    FAIL();
+  } catch (const sourcemeta::core::SchemaKeywordError &error) {
+    EXPECT_STREQ(error.what(), "The identifier is not a valid URI");
+    EXPECT_EQ(error.keyword(), "$id");
+    EXPECT_EQ(error.value(), "//[::44.1");
+  } catch (...) {
+    FAIL();
+  }
+}