diff --git a/package.json b/package.json
index efa8c72..9699403 100644
--- a/package.json
+++ b/package.json
@@ -84,16 +84,16 @@
   ],
   "license": "Apache-2.0",
   "dependencies": {
-    "@eslint/core": "^0.15.2",
+    "@eslint/core": "^0.16.0",
     "@eslint/css-tree": "^3.6.5",
-    "@eslint/plugin-kit": "^0.3.5"
+    "@eslint/plugin-kit": "^0.4.0"
   },
   "devDependencies": {
     "@eslint/json": "^0.13.1",
     "c8": "^10.1.3",
     "compute-baseline": "^0.4.0",
     "dedent": "^1.5.3",
-    "eslint": "^9.35.0",
+    "eslint": "^9.36.0",
     "eslint-config-eslint": "^13.0.0",
     "eslint-plugin-eslint-plugin": "^6.3.2",
     "got": "^14.4.2",
diff --git a/tests/languages/css-source-code.test.js b/tests/languages/css-source-code.test.js
index 635cd41..37e5de9 100644
--- a/tests/languages/css-source-code.test.js
+++ b/tests/languages/css-source-code.test.js
@@ -104,6 +104,236 @@ describe("CSSSourceCode", () => {
 		});
 	});
 
+	describe("getLocFromIndex()", () => {
+		it("should convert index to location correctly", () => {
+			const file = {
+				body: "a {\n  /*test*/\r\n}",
+				path: "test.css",
+			};
+			const language = new CSSLanguage();
+			const parseResult = language.parse(file);
+			const sourceCode = new CSSSourceCode({
+				text: file.body,
+				ast: parseResult.ast,
+			});
+
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(0), {
+				line: 1,
+				column: 1,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(1), {
+				line: 1,
+				column: 2,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(2), {
+				line: 1,
+				column: 3,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(3), {
+				line: 1,
+				column: 4,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(4), {
+				line: 2,
+				column: 1,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(5), {
+				line: 2,
+				column: 2,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(6), {
+				line: 2,
+				column: 3,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(7), {
+				line: 2,
+				column: 4,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(8), {
+				line: 2,
+				column: 5,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(9), {
+				line: 2,
+				column: 6,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(10), {
+				line: 2,
+				column: 7,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(11), {
+				line: 2,
+				column: 8,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(12), {
+				line: 2,
+				column: 9,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(13), {
+				line: 2,
+				column: 10,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(14), {
+				line: 2,
+				column: 11,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(15), {
+				line: 2,
+				column: 12,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(16), {
+				line: 3,
+				column: 1,
+			});
+			assert.deepStrictEqual(sourceCode.getLocFromIndex(17), {
+				line: 3,
+				column: 2,
+			});
+		});
+	});
+
+	describe("getIndexFromLoc()", () => {
+		it("should convert location to index correctly", () => {
+			const file = {
+				body: "a {\n  /*test*/\r\n}",
+				path: "test.css",
+			};
+			const language = new CSSLanguage();
+			const parseResult = language.parse(file);
+			const sourceCode = new CSSSourceCode({
+				text: file.body,
+				ast: parseResult.ast,
+			});
+
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 1,
+					column: 1,
+				}),
+				0,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 1,
+					column: 2,
+				}),
+				1,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 1,
+					column: 3,
+				}),
+				2,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 1,
+					column: 4,
+				}),
+				3,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 1,
+				}),
+				4,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 2,
+				}),
+				5,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 3,
+				}),
+				6,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 4,
+				}),
+				7,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 5,
+				}),
+				8,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 6,
+				}),
+				9,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 7,
+				}),
+				10,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 8,
+				}),
+				11,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 9,
+				}),
+				12,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 10,
+				}),
+				13,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 11,
+				}),
+				14,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 2,
+					column: 12,
+				}),
+				15,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 3,
+					column: 1,
+				}),
+				16,
+			);
+			assert.strictEqual(
+				sourceCode.getIndexFromLoc({
+					line: 3,
+					column: 2,
+				}),
+				17,
+			);
+		});
+	});
+
 	describe("getRange()", () => {
 		it("should return the range property of a node", () => {
 			const loc = {
diff --git a/tests/types/types.test.ts b/tests/types/types.test.ts
index 921e3b7..776de11 100644
--- a/tests/types/types.test.ts
+++ b/tests/types/types.test.ts
@@ -1,5 +1,5 @@
 import css, { CSSSourceCode } from "@eslint/css";
-import { ESLint } from "eslint";
+import type { ESLint } from "eslint";
 import type { SourceLocation, SourceRange } from "@eslint/core";
 import type {
 	AnPlusB,
@@ -82,6 +82,11 @@ css.configs.recommended.plugins satisfies object;
 
 		function testVisitor<NodeType extends CssNodePlain>(node: NodeType) {
 			sourceCode.getLoc(node) satisfies SourceLocation;
+			sourceCode.getLocFromIndex(0) satisfies {
+				line: number;
+				column: number;
+			};
+			sourceCode.getIndexFromLoc({ line: 1, column: 1 }) satisfies number;
 			sourceCode.getRange(node) satisfies SourceRange;
 			sourceCode.getParent(node) satisfies CssNodePlain | undefined;
 			sourceCode.getAncestors(node) satisfies CssNodePlain[];