diff --git a/index.d.ts b/index.d.ts
index 9d762db..ec23bed 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -10,7 +10,17 @@ export interface SourceMapOptions {
   includeContent: boolean;
 }
 
-export interface SourceMap {
+export interface DecodedSourceMap {
+  file: string;
+  sources: string[];
+  sourcesContent: string[];
+  names: string[];
+  mappings: number[][][];
+}
+
+export class SourceMap {
+  constructor(properties: DecodedSourceMap);
+
   version: string;
   file: string;
   sources: string[];
@@ -28,6 +38,7 @@ export class Bundle {
   append(str: string, options?: BundleOptions): Bundle;
   clone(): Bundle;
   generateMap(options?: Partial<SourceMapOptions>): SourceMap;
+  generateDecodedMap(options?: Partial<SourceMapOptions>): DecodedSourceMap;
   getIndentString(): string;
   indent(indentStr?: string): Bundle;
   indentExclusionRanges: ExclusionRange | Array<ExclusionRange>;
@@ -64,6 +75,7 @@ export default class MagicString {
   appendRight(index: number, content: string): MagicString;
   clone(): MagicString;
   generateMap(options?: Partial<SourceMapOptions>): SourceMap;
+  generateDecodedMap(options?: Partial<SourceMapOptions>): DecodedSourceMap;
   getIndentString(): string;
 
   indent(options?: IndentOptions): MagicString;
diff --git a/src/Bundle.js b/src/Bundle.js
index 8a11683..02ee934 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -80,7 +80,7 @@ Bundle.prototype = {
 		return bundle;
 	},
 
-	generateMap ( options = {} ) {
+	generateDecodedMap ( options = {} ) {
 		const names = [];
 		this.sources.forEach( source => {
 			Object.keys( source.content.storedNames ).forEach( name => {
@@ -114,7 +114,7 @@ Bundle.prototype = {
 
 				if ( source.filename ) {
 					if ( chunk.edited ) {
-						mappings.addEdit( sourceIndex, chunk.content, chunk.original, loc, chunk.storeName ? names.indexOf( chunk.original ) : -1 );
+						mappings.addEdit( sourceIndex, chunk.content, loc, chunk.storeName ? names.indexOf( chunk.original ) : -1 );
 					} else {
 						mappings.addUneditedChunk( sourceIndex, chunk, magicString.original, loc, magicString.sourcemapLocations );
 					}
@@ -132,7 +132,7 @@ Bundle.prototype = {
 			}
 		});
 
-		return new SourceMap({
+		return {
 			file: ( options.file ? options.file.split( /[\/\\]/ ).pop() : null ),
 			sources: this.uniqueSources.map( source => {
 				return options.file ? getRelativePath( options.file, source.filename ) : source.filename;
@@ -141,8 +141,12 @@ Bundle.prototype = {
 				return options.includeContent ? source.content : null;
 			}),
 			names,
-			mappings: mappings.encode()
-		});
+			mappings: mappings.raw
+		};
+	},
+
+	generateMap ( options ) {
+		return new SourceMap(this.generateDecodedMap( options ));
 	},
 
 	getIndentString () {
diff --git a/src/MagicString.js b/src/MagicString.js
index ea3b36e..1b435c9 100644
--- a/src/MagicString.js
+++ b/src/MagicString.js
@@ -1,3 +1,4 @@
+import { encode } from 'sourcemap-codec';
 import Chunk from './Chunk.js';
 import SourceMap from './utils/SourceMap.js';
 import guessIndent from './utils/guessIndent.js';
@@ -126,7 +127,7 @@ MagicString.prototype = {
 		return cloned;
 	},
 
-	generateMap ( options ) {
+	generateDecodedMap ( options ) {
 		options = options || {};
 
 		const sourceIndex = 0;
@@ -145,7 +146,7 @@ MagicString.prototype = {
 			if ( chunk.intro.length ) mappings.advance( chunk.intro );
 
 			if ( chunk.edited ) {
-				mappings.addEdit( sourceIndex, chunk.content, chunk.original, loc, chunk.storeName ? names.indexOf( chunk.original ) : -1 );
+				mappings.addEdit( sourceIndex, chunk.content, loc, chunk.storeName ? names.indexOf( chunk.original ) : -1 );
 			} else {
 				mappings.addUneditedChunk( sourceIndex, chunk, this.original, loc, this.sourcemapLocations );
 			}
@@ -153,17 +154,17 @@ MagicString.prototype = {
 			if ( chunk.outro.length ) mappings.advance( chunk.outro );
 		});
 
-		if ( DEBUG ) this.stats.time( 'generateMap' );
-		const map = new SourceMap({
+		return {
 			file: ( options.file ? options.file.split( /[\/\\]/ ).pop() : null ),
 			sources: [ options.source ? getRelativePath( options.file || '', options.source ) : null ],
 			sourcesContent: options.includeContent ? [ this.original ] : [ null ],
 			names,
-			mappings: mappings.encode()
-		});
-		if ( DEBUG ) this.stats.timeEnd( 'generateMap' );
+			mappings: mappings.raw
+		};
+	},
 
-		return map;
+	generateMap ( options ) {
+		return new SourceMap(this.generateDecodedMap( options ));
 	},
 
 	getIndentString () {
diff --git a/src/index.js b/src/index.js
index 594d8db..44c15ef 100644
--- a/src/index.js
+++ b/src/index.js
@@ -2,3 +2,4 @@ import MagicString from './MagicString.js';
 
 export default MagicString;
 export { default as Bundle } from './Bundle.js';
+export { default as SourceMap} from './utils/SourceMap.js';
diff --git a/src/utils/Mappings.js b/src/utils/Mappings.js
index fead3a9..bcd1377 100644
--- a/src/utils/Mappings.js
+++ b/src/utils/Mappings.js
@@ -1,5 +1,3 @@
-import { encode } from 'sourcemap-codec';
-
 export default function Mappings ( hires ) {
 	let generatedCodeLine = 0;
 	let generatedCodeColumn = 0;
@@ -9,7 +7,7 @@ export default function Mappings ( hires ) {
 
 	let pending = null;
 
-	this.addEdit = ( sourceIndex, content, original, loc, nameIndex ) => {
+	this.addEdit = ( sourceIndex, content, loc, nameIndex ) => {
 		if ( content.length ) {
 			const segment = [
 				generatedCodeColumn,
@@ -81,8 +79,4 @@ export default function Mappings ( hires ) {
 
 		generatedCodeColumn += lines[lines.length - 1].length;
 	};
-
-	this.encode = () => {
-		return encode(this.raw);
-	};
 }
diff --git a/src/utils/SourceMap.js b/src/utils/SourceMap.js
index f3dde82..3117b88 100644
--- a/src/utils/SourceMap.js
+++ b/src/utils/SourceMap.js
@@ -1,4 +1,5 @@
 import btoa from './btoa.js';
+import { encode } from 'sourcemap-codec';
 
 export default function SourceMap ( properties ) {
 	this.version = 3;
@@ -7,7 +8,7 @@ export default function SourceMap ( properties ) {
 	this.sources        = properties.sources;
 	this.sourcesContent = properties.sourcesContent;
 	this.names          = properties.names;
-	this.mappings       = properties.mappings;
+	this.mappings       = encode(properties.mappings);
 }
 
 SourceMap.prototype = {