diff --git a/ext/bg/js/json-schema.js b/ext/bg/js/json-schema.js
index b777ac09..7cc87bb0 100644
--- a/ext/bg/js/json-schema.js
+++ b/ext/bg/js/json-schema.js
@@ -326,6 +326,11 @@ class JsonSchemaValidator {
             throw new JsonSchemaValidationError(`Value type ${type} does not match schema type ${schemaType}`, value, schema, info);
         }
 
+        const schemaConst = schema.const;
+        if (typeof schemaConst !== 'undefined' && !this.valuesAreEqual(value, schemaConst)) {
+            throw new JsonSchemaValidationError('Invalid constant value', value, schema, info);
+        }
+
         const schemaEnum = schema.enum;
         if (Array.isArray(schemaEnum) && !this.valuesAreEqualAny(value, schemaEnum)) {
             throw new JsonSchemaValidationError('Invalid enum value', value, schema, info);
@@ -414,6 +419,8 @@ class JsonSchemaValidator {
             throw new JsonSchemaValidationError('Array length too long', value, schema, info);
         }
 
+        this.validateArrayContains(value, schema, info);
+
         for (let i = 0, ii = value.length; i < ii; ++i) {
             const schemaPath = [];
             const propertySchema = this.getPropertySchema(schema, i, value, schemaPath);
@@ -431,6 +438,26 @@ class JsonSchemaValidator {
         }
     }
 
+    validateArrayContains(value, schema, info) {
+        const containsSchema = schema.contains;
+        if (!this.isObject(containsSchema)) { return; }
+
+        info.schemaPush('contains', containsSchema);
+        for (let i = 0, ii = value.length; i < ii; ++i) {
+            const propertyValue = value[i];
+            info.valuePush(i, propertyValue);
+            try {
+                this.validate(propertyValue, containsSchema, info);
+                info.schemaPop();
+                return;
+            } catch (e) {
+                // NOP
+            }
+            info.valuePop();
+        }
+        throw new JsonSchemaValidationError('contains schema didn\'t match', value, schema, info);
+    }
+
     validateObject(value, schema, info) {
         const properties = new Set(Object.getOwnPropertyNames(value));
 
diff --git a/test/test-schema.js b/test/test-schema.js
index b976d81f..b3544b28 100644
--- a/test/test-schema.js
+++ b/test/test-schema.js
@@ -185,6 +185,212 @@ function testValidate2() {
             inputs: [
                 {expected: false, value: ''}
             ]
+        },
+
+        // Const tests
+        {
+            schema: {
+                const: 32
+            },
+            inputs: [
+                {expected: true,  value: 32},
+                {expected: false, value: 0},
+                {expected: false, value: '32'},
+                {expected: false, value: null},
+                {expected: false, value: {a: 'b'}},
+                {expected: false, value: [1, 2, 3]}
+            ]
+        },
+        {
+            schema: {
+                const: '32'
+            },
+            inputs: [
+                {expected: false, value: 32},
+                {expected: false, value: 0},
+                {expected: true,  value: '32'},
+                {expected: false, value: null},
+                {expected: false, value: {a: 'b'}},
+                {expected: false, value: [1, 2, 3]}
+            ]
+        },
+        {
+            schema: {
+                const: null
+            },
+            inputs: [
+                {expected: false, value: 32},
+                {expected: false, value: 0},
+                {expected: false, value: '32'},
+                {expected: true,  value: null},
+                {expected: false, value: {a: 'b'}},
+                {expected: false, value: [1, 2, 3]}
+            ]
+        },
+        {
+            schema: {
+                const: {a: 'b'}
+            },
+            inputs: [
+                {expected: false, value: 32},
+                {expected: false, value: 0},
+                {expected: false, value: '32'},
+                {expected: false, value: null},
+                {expected: false, value: {a: 'b'}},
+                {expected: false, value: [1, 2, 3]}
+            ]
+        },
+        {
+            schema: {
+                const: [1, 2, 3]
+            },
+            inputs: [
+                {expected: false, value: 32},
+                {expected: false, value: 0},
+                {expected: false,  value: '32'},
+                {expected: false, value: null},
+                {expected: false, value: {a: 'b'}},
+                {expected: false, value: [1, 2, 3]}
+            ]
+        },
+
+        // Array contains tests
+        {
+            schema: {
+                type: 'array',
+                contains: {const: 32}
+            },
+            inputs: [
+                {expected: false, value: []},
+                {expected: true,  value: [32]},
+                {expected: true,  value: [1, 32]},
+                {expected: true,  value: [1, 32, 1]},
+                {expected: false, value: [33]},
+                {expected: false, value: [1, 33]},
+                {expected: false, value: [1, 33, 1]}
+            ]
+        },
+
+        // Number limits tests
+        {
+            schema: {
+                type: 'number',
+                minimum: 0
+            },
+            inputs: [
+                {expected: false, value: -1},
+                {expected: true,  value: 0},
+                {expected: true,  value: 1}
+            ]
+        },
+        {
+            schema: {
+                type: 'number',
+                exclusiveMinimum: 0
+            },
+            inputs: [
+                {expected: false, value: -1},
+                {expected: false, value: 0},
+                {expected: true,  value: 1}
+            ]
+        },
+        {
+            schema: {
+                type: 'number',
+                maximum: 0
+            },
+            inputs: [
+                {expected: true,  value: -1},
+                {expected: true,  value: 0},
+                {expected: false, value: 1}
+            ]
+        },
+        {
+            schema: {
+                type: 'number',
+                exclusiveMaximum: 0
+            },
+            inputs: [
+                {expected: true,  value: -1},
+                {expected: false, value: 0},
+                {expected: false, value: 1}
+            ]
+        },
+
+        // Integer limits tests
+        {
+            schema: {
+                type: 'integer',
+                minimum: 0
+            },
+            inputs: [
+                {expected: false, value: -1},
+                {expected: true,  value: 0},
+                {expected: true,  value: 1}
+            ]
+        },
+        {
+            schema: {
+                type: 'integer',
+                exclusiveMinimum: 0
+            },
+            inputs: [
+                {expected: false, value: -1},
+                {expected: false, value: 0},
+                {expected: true,  value: 1}
+            ]
+        },
+        {
+            schema: {
+                type: 'integer',
+                maximum: 0
+            },
+            inputs: [
+                {expected: true,  value: -1},
+                {expected: true,  value: 0},
+                {expected: false, value: 1}
+            ]
+        },
+        {
+            schema: {
+                type: 'integer',
+                exclusiveMaximum: 0
+            },
+            inputs: [
+                {expected: true,  value: -1},
+                {expected: false, value: 0},
+                {expected: false, value: 1}
+            ]
+        },
+
+        // Numeric type tests
+        {
+            schema: {
+                type: 'number'
+            },
+            inputs: [
+                {expected: true,  value: 0},
+                {expected: true,  value: 0.5},
+                {expected: true,  value: 1},
+                {expected: false, value: '0'},
+                {expected: false, value: null},
+                {expected: false, value: []},
+                {expected: false, value: {}}
+            ]
+        },
+        {
+            schema: {
+                type: 'integer'
+            },
+            inputs: [
+                {expected: true,  value: 0},
+                {expected: false, value: 0.5},
+                {expected: true,  value: 1},
+                {expected: false, value: '0'},
+                {expected: false, value: null},
+                {expected: false, value: []},
+                {expected: false, value: {}}
+            ]
         }
     ];
 
@@ -207,158 +413,151 @@ function testValidate2() {
 
 
 function testGetValidValueOrDefault1() {
-    // Test value defaulting on objects with additionalProperties=false
-    const schema = {
-        type: 'object',
-        required: ['test'],
-        properties: {
-            test: {
-                type: 'string',
-                default: 'default'
-            }
+    const data = [
+        // Test value defaulting on objects with additionalProperties=false
+        {
+            schema: {
+                type: 'object',
+                required: ['test'],
+                properties: {
+                    test: {
+                        type: 'string',
+                        default: 'default'
+                    }
+                },
+                additionalProperties: false
+            },
+            inputs: [
+                [
+                    void 0,
+                    {test: 'default'}
+                ],
+                [
+                    null,
+                    {test: 'default'}
+                ],
+                [
+                    0,
+                    {test: 'default'}
+                ],
+                [
+                    '',
+                    {test: 'default'}
+                ],
+                [
+                    [],
+                    {test: 'default'}
+                ],
+                [
+                    {},
+                    {test: 'default'}
+                ],
+                [
+                    {test: 'value'},
+                    {test: 'value'}
+                ],
+                [
+                    {test2: 'value2'},
+                    {test: 'default'}
+                ],
+                [
+                    {test: 'value', test2: 'value2'},
+                    {test: 'value'}
+                ]
+            ]
         },
-        additionalProperties: false
-    };
 
-    const testData = [
-        [
-            void 0,
-            {test: 'default'}
-        ],
-        [
-            null,
-            {test: 'default'}
-        ],
-        [
-            0,
-            {test: 'default'}
-        ],
-        [
-            '',
-            {test: 'default'}
-        ],
-        [
-            [],
-            {test: 'default'}
-        ],
-        [
-            {},
-            {test: 'default'}
-        ],
-        [
-            {test: 'value'},
-            {test: 'value'}
-        ],
-        [
-            {test2: 'value2'},
-            {test: 'default'}
-        ],
-        [
-            {test: 'value', test2: 'value2'},
-            {test: 'value'}
-        ]
-    ];
-
-    for (const [value, expected] of testData) {
-        const actual = JsonSchema.getValidValueOrDefault(schema, value);
-        vm.assert.deepStrictEqual(actual, expected);
-    }
-}
-
-function testGetValidValueOrDefault2() {
-    // Test value defaulting on objects with additionalProperties=true
-    const schema = {
-        type: 'object',
-        required: ['test'],
-        properties: {
-            test: {
-                type: 'string',
-                default: 'default'
-            }
+        // Test value defaulting on objects with additionalProperties=true
+        {
+            schema: {
+                type: 'object',
+                required: ['test'],
+                properties: {
+                    test: {
+                        type: 'string',
+                        default: 'default'
+                    }
+                },
+                additionalProperties: true
+            },
+            inputs: [
+                [
+                    {},
+                    {test: 'default'}
+                ],
+                [
+                    {test: 'value'},
+                    {test: 'value'}
+                ],
+                [
+                    {test2: 'value2'},
+                    {test: 'default', test2: 'value2'}
+                ],
+                [
+                    {test: 'value', test2: 'value2'},
+                    {test: 'value', test2: 'value2'}
+                ]
+            ]
         },
-        additionalProperties: true
-    };
 
-    const testData = [
-        [
-            {},
-            {test: 'default'}
-        ],
-        [
-            {test: 'value'},
-            {test: 'value'}
-        ],
-        [
-            {test2: 'value2'},
-            {test: 'default', test2: 'value2'}
-        ],
-        [
-            {test: 'value', test2: 'value2'},
-            {test: 'value', test2: 'value2'}
-        ]
-    ];
-
-    for (const [value, expected] of testData) {
-        const actual = JsonSchema.getValidValueOrDefault(schema, value);
-        vm.assert.deepStrictEqual(actual, expected);
-    }
-}
-
-function testGetValidValueOrDefault3() {
-    // Test value defaulting on objects with additionalProperties={schema}
-    const schema = {
-        type: 'object',
-        required: ['test'],
-        properties: {
-            test: {
-                type: 'string',
-                default: 'default'
-            }
-        },
-        additionalProperties: {
-            type: 'number',
-            default: 10
+        // Test value defaulting on objects with additionalProperties={schema}
+        {
+            schema: {
+                type: 'object',
+                required: ['test'],
+                properties: {
+                    test: {
+                        type: 'string',
+                        default: 'default'
+                    }
+                },
+                additionalProperties: {
+                    type: 'number',
+                    default: 10
+                }
+            },
+            inputs: [
+                [
+                    {},
+                    {test: 'default'}
+                ],
+                [
+                    {test: 'value'},
+                    {test: 'value'}
+                ],
+                [
+                    {test2: 'value2'},
+                    {test: 'default', test2: 10}
+                ],
+                [
+                    {test: 'value', test2: 'value2'},
+                    {test: 'value', test2: 10}
+                ],
+                [
+                    {test2: 2},
+                    {test: 'default', test2: 2}
+                ],
+                [
+                    {test: 'value', test2: 2},
+                    {test: 'value', test2: 2}
+                ],
+                [
+                    {test: 'value', test2: 2, test3: null},
+                    {test: 'value', test2: 2, test3: 10}
+                ],
+                [
+                    {test: 'value', test2: 2, test3: void 0},
+                    {test: 'value', test2: 2, test3: 10}
+                ]
+            ]
         }
-    };
-
-    const testData = [
-        [
-            {},
-            {test: 'default'}
-        ],
-        [
-            {test: 'value'},
-            {test: 'value'}
-        ],
-        [
-            {test2: 'value2'},
-            {test: 'default', test2: 10}
-        ],
-        [
-            {test: 'value', test2: 'value2'},
-            {test: 'value', test2: 10}
-        ],
-        [
-            {test2: 2},
-            {test: 'default', test2: 2}
-        ],
-        [
-            {test: 'value', test2: 2},
-            {test: 'value', test2: 2}
-        ],
-        [
-            {test: 'value', test2: 2, test3: null},
-            {test: 'value', test2: 2, test3: 10}
-        ],
-        [
-            {test: 'value', test2: 2, test3: void 0},
-            {test: 'value', test2: 2, test3: 10}
-        ]
     ];
 
-    for (const [value, expected] of testData) {
-        const actual = JsonSchema.getValidValueOrDefault(schema, value);
-        vm.assert.deepStrictEqual(actual, expected);
+    for (const {schema, inputs} of data) {
+        for (const [value, expected] of inputs) {
+            const actual = JsonSchema.getValidValueOrDefault(schema, value);
+            vm.assert.deepStrictEqual(actual, expected);
+        }
     }
 }
 
@@ -367,8 +566,6 @@ function main() {
     testValidate1();
     testValidate2();
     testGetValidValueOrDefault1();
-    testGetValidValueOrDefault2();
-    testGetValidValueOrDefault3();
 }