diff --git a/index.d.ts b/index.d.ts
index 2ffe0e9..2ec2bba 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -38,6 +38,7 @@ export interface DecodedSourceMap {
   sourcesContent: (string | null)[];
   names: string[];
   mappings: SourceMapSegment[][];
+  x_google_ignoreList?: number[];
 }
 
 export class SourceMap {
@@ -49,6 +50,7 @@ export class SourceMap {
   sourcesContent: (string | null)[];
   names: string[];
   mappings: string;
+  x_google_ignoreList?: number[];
 
   /**
    * Returns the equivalent of `JSON.stringify(map)`
diff --git a/src/SourceMap.js b/src/SourceMap.js
index feb1e02..9389315 100644
--- a/src/SourceMap.js
+++ b/src/SourceMap.js
@@ -22,6 +22,9 @@ export default class SourceMap {
 		this.sourcesContent = properties.sourcesContent;
 		this.names = properties.names;
 		this.mappings = encode(properties.mappings);
+		if (typeof properties.x_google_ignoreList !== 'undefined') {
+			this.x_google_ignoreList = properties.x_google_ignoreList;
+		}
 	}
 
 	toString() {
diff --git a/test/MagicString.SourceMap.js b/test/MagicString.SourceMap.js
new file mode 100644
index 0000000..257b010
--- /dev/null
+++ b/test/MagicString.SourceMap.js
@@ -0,0 +1,36 @@
+const assert = require('assert');
+const MagicString = require('../');
+
+require('source-map-support').install();
+
+describe('MagicString.SourceMap', () => {
+	describe('options', () => {
+		it('preserves ignore list information', () => {
+			const map = new MagicString.SourceMap({
+				file: 'foo.min.js',
+				sources: ['foo.js'],
+				sourcesContent: ['42'],
+				names: [],
+				mappings: [[0, 0]],
+				x_google_ignoreList: [0]
+			});
+
+			assert.deepEqual(map.x_google_ignoreList, [0]);
+		});
+	});
+
+	describe('toString', () => {
+		it('serializes ignore list information', () => {
+			const map = new MagicString.SourceMap({
+				file: 'foo.min.js',
+				sources: ['foo.js'],
+				sourcesContent: ['42'],
+				names: [],
+				mappings: [[0, 0]],
+				x_google_ignoreList: [0]
+			});
+
+			assert.equal(map.toString(), '{"version":3,"file":"foo.min.js","sources":["foo.js"],"sourcesContent":["42"],"names":[],"mappings":"AAAAA,AAAAA","x_google_ignoreList":[0]}');
+		});
+	});
+});