diff --git a/packages/metro/src/Bundler/index.js b/packages/metro/src/Bundler/index.js
index 4b7c56ef..5b8e208c 100644
--- a/packages/metro/src/Bundler/index.js
+++ b/packages/metro/src/Bundler/index.js
@@ -35,7 +35,7 @@ import type {HasteImpl} from '../node-haste/Module';
 import type {BabelSourceMap} from 'babel-core';
 import type {
   MetroSourceMapSegmentTuple,
-  MetroSourceMap as SourceMap,
+  MetroSourceMap,
 } from 'metro-source-map';
 
 export type BundlingOptions = {|
@@ -73,9 +73,9 @@ export type PostMinifyProcess = ({
 
 export type PostProcessBundleSourcemap = ({
   code: Buffer | string,
-  map: SourceMap,
+  map: MetroSourceMap,
   outFileName: string,
-}) => {code: Buffer | string, map: SourceMap | string};
+}) => {code: Buffer | string, map: MetroSourceMap | string};
 
 export type Options = {|
   +assetExts: Array<string>,
diff --git a/packages/metro/src/ModuleGraph/types.flow.js b/packages/metro/src/ModuleGraph/types.flow.js
index acd1a4ba..2df3bc39 100644
--- a/packages/metro/src/ModuleGraph/types.flow.js
+++ b/packages/metro/src/ModuleGraph/types.flow.js
@@ -14,7 +14,7 @@
 import type {Ast} from 'babel-core';
 import type {BabelSourceMap} from 'babel-core';
 import type {Console} from 'console';
-import type {FBSourceMap, MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {FBSourceMap, MetroSourceMap} from 'metro-source-map';
 
 export type {Transformer} from '../JSTransformer/worker';
 
@@ -106,7 +106,9 @@ export type PostProcessModules = (
   entryPoints: Array<string>,
 ) => Iterable<Module>;
 
-export type OutputFn<M: FBSourceMap | SourceMap = FBSourceMap | SourceMap> = ({|
+export type OutputFn<
+  M: FBSourceMap | MetroSourceMap = FBSourceMap | MetroSourceMap,
+> = ({|
   filename: string,
   idsForPath: IdsForPathFn,
   modules: Iterable<Module>,
@@ -114,7 +116,7 @@ export type OutputFn<M: FBSourceMap | SourceMap = FBSourceMap | SourceMap> = ({|
   sourceMapPath?: ?string,
 |}) => OutputResult<M>;
 
-type OutputResult<M: FBSourceMap | SourceMap> = {|
+type OutputResult<M: FBSourceMap | MetroSourceMap> = {|
   code: string | Buffer,
   extraFiles?: Iterable<[string, string | Buffer]>,
   map: M,
diff --git a/packages/metro/src/ModuleGraph/worker/optimize-module.js b/packages/metro/src/ModuleGraph/worker/optimize-module.js
index 0a3283e2..a1b08c53 100644
--- a/packages/metro/src/ModuleGraph/worker/optimize-module.js
+++ b/packages/metro/src/ModuleGraph/worker/optimize-module.js
@@ -24,7 +24,7 @@ const sourceMap = require('source-map');
 
 import type {TransformedSourceFile, TransformResult} from '../types.flow';
 import type {BabelSourceMap} from 'babel-core';
-import type {MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {MetroSourceMap} from 'metro-source-map';
 import type {PostMinifyProcess} from '../../Bundler/index.js';
 
 export type OptimizationOptions = {|
@@ -111,8 +111,8 @@ function optimizeCode(code, map, filename, inliningOptions) {
 
 function mergeSourceMaps(
   file: string,
-  originalMap: SourceMap,
-  secondMap: SourceMap,
+  originalMap: MetroSourceMap,
+  secondMap: MetroSourceMap,
 ): BabelSourceMap {
   const merged = new sourceMap.SourceMapGenerator();
   const inputMap = new sourceMap.SourceMapConsumer(originalMap);
diff --git a/packages/metro/src/Server/index.js b/packages/metro/src/Server/index.js
index 1d945962..083b1699 100644
--- a/packages/metro/src/Server/index.js
+++ b/packages/metro/src/Server/index.js
@@ -40,7 +40,7 @@ import type {
   PostMinifyProcess,
   PostProcessBundleSourcemap,
 } from '../Bundler';
-import type {MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {MetroSourceMap} from 'metro-source-map';
 import type {TransformCache} from '../lib/TransformCaching';
 import type {Symbolicate} from './symbolicate';
 import type {AssetData} from '../Assets';
@@ -731,7 +731,7 @@ class Server {
       );
   }
 
-  async _sourceMapForURL(reqUrl: string): Promise<SourceMap> {
+  async _sourceMapForURL(reqUrl: string): Promise<MetroSourceMap> {
     const options: DeltaBundlerOptions = this._getOptionsFromUrl(reqUrl);
 
     return await Serializers.fullSourceMapObject(this._deltaBundler, {
diff --git a/packages/metro/src/Server/symbolicate/symbolicate.js b/packages/metro/src/Server/symbolicate/symbolicate.js
index d709aed6..0209aa50 100644
--- a/packages/metro/src/Server/symbolicate/symbolicate.js
+++ b/packages/metro/src/Server/symbolicate/symbolicate.js
@@ -20,12 +20,12 @@ const xpipe = require('xpipe');
 const {LazyPromise, LockingPromise} = require('./util');
 const {fork} = require('child_process');
 
-import type {MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {MetroSourceMap} from 'metro-source-map';
 
 export type Stack = Array<{file: string, lineNumber: number, column: number}>;
 export type Symbolicate = (
   Stack,
-  Iterable<[string, SourceMap]>,
+  Iterable<[string, MetroSourceMap]>,
 ) => Promise<Stack>;
 
 const affixes = {prefix: 'metro-symbolicate', suffix: '.sock'};
diff --git a/packages/metro/src/lib/relativizeSourceMap.js b/packages/metro/src/lib/relativizeSourceMap.js
index 9485fb42..03a4d5e7 100644
--- a/packages/metro/src/lib/relativizeSourceMap.js
+++ b/packages/metro/src/lib/relativizeSourceMap.js
@@ -14,10 +14,10 @@
 
 const path = require('path');
 
-import type {MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {MetroSourceMap} from 'metro-source-map';
 
 function relativizeSourceMapInternal(
-  sourceMap: SourceMap,
+  sourceMap: MetroSourceMap,
   sourcesRoot: string,
 ) {
   if (sourceMap.mappings === undefined) {
@@ -32,9 +32,9 @@ function relativizeSourceMapInternal(
 }
 
 function relativizeSourceMap(
-  sourceMap: SourceMap,
+  sourceMap: MetroSourceMap,
   sourcesRoot?: string,
-): SourceMap {
+): MetroSourceMap {
   if (!sourcesRoot) {
     return sourceMap;
   }
diff --git a/packages/metro/src/shared/output/bundle.js b/packages/metro/src/shared/output/bundle.js
index 26fab8b7..2dff183a 100644
--- a/packages/metro/src/shared/output/bundle.js
+++ b/packages/metro/src/shared/output/bundle.js
@@ -20,7 +20,7 @@ const relativizeSourceMap = require('../../lib/relativizeSourceMap');
 const writeFile = require('./writeFile');
 
 import type {OutputOptions, RequestOptions} from '../types.flow';
-import type {MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {MetroSourceMap} from 'metro-source-map';
 
 function buildBundle(
   packagerClient: Server,
@@ -38,10 +38,10 @@ function createCodeWithMap(
   bundle: {code: string, map: string},
   dev: boolean,
   sourceMapSourcesRoot?: string,
-): {code: string, map: SourceMap} {
+): {code: string, map: MetroSourceMap} {
   const map = bundle.map;
   const sourceMap = relativizeSourceMap(
-    (JSON.parse(map): SourceMap),
+    (JSON.parse(map): MetroSourceMap),
     sourceMapSourcesRoot,
   );
   return {
diff --git a/packages/metro/src/shared/output/unbundle/util.js b/packages/metro/src/shared/output/unbundle/util.js
index 6bf8111c..6cc85a91 100644
--- a/packages/metro/src/shared/output/unbundle/util.js
+++ b/packages/metro/src/shared/output/unbundle/util.js
@@ -16,11 +16,7 @@ const invariant = require('fbjs/lib/invariant');
 import type {RamModule} from '../../../DeltaBundler/Serializers';
 import type {ModuleGroups, ModuleTransportLike} from '../../types.flow';
 import type {BabelSourceMap} from 'babel-core';
-import type {
-  FBIndexMap,
-  IndexMap,
-  MetroSourceMap as SourceMap,
-} from 'metro-source-map';
+import type {FBIndexMap, IndexMap, MetroSourceMap} from 'metro-source-map';
 
 const newline = /\r\n?|\n|\u2028|\u2029/g;
 // fastest implementation
@@ -48,7 +44,7 @@ function lineToLineSourceMap(
 
 const wrapperEnd = wrappedCode => wrappedCode.indexOf('{') + 1;
 
-const Section = (line: number, column: number, map: SourceMap) => ({
+const Section = (line: number, column: number, map: MetroSourceMap) => ({
   map,
   offset: {line, column},
 });
diff --git a/packages/metro/src/shared/types.flow.js b/packages/metro/src/shared/types.flow.js
index 1f3e9f0a..731c011b 100644
--- a/packages/metro/src/shared/types.flow.js
+++ b/packages/metro/src/shared/types.flow.js
@@ -22,12 +22,12 @@ import type {TransformCache} from '../lib/TransformCaching';
 import type {Reporter} from '../lib/reporting';
 import type {HasteImpl} from '../node-haste/Module';
 import type {
-  MetroSourceMap as SourceMap,
+  MetroSourceMap,
   MetroSourceMapSegmentTuple,
 } from 'metro-source-map';
 
 type BundleType = 'bundle' | 'delta' | 'map' | 'ram' | 'cli' | 'hmr' | 'todo';
-type SourceMapOrMappings = SourceMap | Array<MetroSourceMapSegmentTuple>;
+type SourceMapOrMappings = MetroSourceMap | Array<MetroSourceMapSegmentTuple>;
 
 export type BundleOptions = {
   +assetPlugins: Array<string>,