diff --git a/flow-typed/babel.js.flow b/flow-typed/babel.js.flow
index 810c0b1c..d6bbab44 100644
--- a/flow-typed/babel.js.flow
+++ b/flow-typed/babel.js.flow
@@ -10,7 +10,7 @@
  * @format
  */
 
-type _SourceMap = {
+type _BabelSourceMap = {
   file?: string,
   mappings: string,
   names: Array<string>,
@@ -108,19 +108,19 @@ type TransformResult = {
   ast: Ast,
   code: ?string,
   ignored: boolean,
-  map: ?_SourceMap,
+  map: ?_BabelSourceMap,
 };
 // https://github.com/babel/babel/blob/master/packages/babel-generator/src/buffer.js#L42
 type GeneratorResult = {
   code: string,
-  map: ?_SourceMap,
+  map: ?_BabelSourceMap,
   rawMappings: ?Array<_RawMapping>,
 };
 type VisitFn = <State>(path: Object, state: State) => any;
 
 declare module 'babel-core' {
   declare type Plugins = _Plugins;
-  declare type SourceMap = _SourceMap;
+  declare type BabelSourceMap = _BabelSourceMap;
   declare type Ast = {};
   declare type TransformOptions = _TransformOptions;
   declare function transform(
diff --git a/packages/metro-source-map/src/Generator.js b/packages/metro-source-map/src/Generator.js
index f08b359e..8cb571c9 100644
--- a/packages/metro-source-map/src/Generator.js
+++ b/packages/metro-source-map/src/Generator.js
@@ -14,7 +14,7 @@
 
 const B64Builder = require('./B64Builder');
 
-import type {SourceMap as MappingsMap} from 'babel-core';
+import type {BabelSourceMap} from 'babel-core';
 
 /**
  * Generates a source map from raw mappings.
@@ -149,7 +149,7 @@ class Generator {
   /**
    * Return the source map as object.
    */
-  toMap(file?: string, options: {excludeSource?: boolean}): MappingsMap {
+  toMap(file?: string, options: {excludeSource?: boolean}): BabelSourceMap {
     let content;
 
     if (options && options.excludeSource) {
diff --git a/packages/metro-source-map/src/source-map.js b/packages/metro-source-map/src/source-map.js
index 72fa0894..5e5ce15e 100644
--- a/packages/metro-source-map/src/source-map.js
+++ b/packages/metro-source-map/src/source-map.js
@@ -15,12 +15,11 @@
 const Generator = require('./Generator');
 const SourceMap = require('source-map');
 
-import type {SourceMap as MappingsMap} from 'babel-core';
+import type {BabelSourceMap} from 'babel-core';
 import type {RawMapping as BabelRawMapping} from 'babel-generator';
-import type {RawMapping as CompactRawMapping} from 'source-map';
+import type {RawMapping as UnknownSourceMapMappingType} from 'source-map';
 
-export type {SourceMap as MappingsMap} from 'babel-core';
-export type CompactRawMappings = Array<CompactRawMapping>;
+export type UnknownSourceMapMappingTypes = Array<UnknownSourceMapMappingType>;
 export type RawMappings = Array<BabelRawMapping>;
 
 type GeneratedCodeMapping = [number, number];
@@ -50,8 +49,8 @@ export type IndexMap = {
 };
 
 export type FBIndexMap = IndexMap & FBExtensions;
-export type MetroSourceMap = IndexMap | MappingsMap;
-export type FBSourceMap = FBIndexMap | (MappingsMap & FBExtensions);
+export type MetroSourceMap = IndexMap | BabelSourceMap;
+export type FBSourceMap = FBIndexMap | (BabelSourceMap & FBExtensions);
 
 /**
  * Creates a source map from modules with "raw mappings", i.e. an array of
@@ -91,7 +90,7 @@ function fromRawMappings(
  * Transforms a standard source map object into a Raw Mappings object, to be
  * used across the bundler.
  */
-function toRawMappings(sourceMap: MappingsMap): RawMappings {
+function toRawMappings(sourceMap: BabelSourceMap): RawMappings {
   const rawMappings = [];
 
   new SourceMap.SourceMapConsumer(sourceMap).eachMapping(map => {
diff --git a/packages/metro/src/Bundler/index.js b/packages/metro/src/Bundler/index.js
index c59f54d8..788ca39f 100644
--- a/packages/metro/src/Bundler/index.js
+++ b/packages/metro/src/Bundler/index.js
@@ -32,9 +32,9 @@ import type {GlobalTransformCache} from '../lib/GlobalTransformCache';
 import type {TransformCache} from '../lib/TransformCaching';
 import type {Reporter} from '../lib/reporting';
 import type {HasteImpl} from '../node-haste/Module';
+import type {BabelSourceMap} from 'babel-core';
 import type {
-  CompactRawMappings,
-  MappingsMap,
+  UnknownSourceMapMappingTypes,
   MetroSourceMap as SourceMap,
 } from 'metro-source-map';
 
@@ -68,8 +68,8 @@ export type GetTransformOptions = (
 
 export type PostMinifyProcess = ({
   code: string,
-  map: ?MappingsMap,
-}) => {code: string, map: ?MappingsMap};
+  map: ?BabelSourceMap,
+}) => {code: string, map: ?BabelSourceMap};
 
 export type PostProcessBundleSourcemap = ({
   code: Buffer | string,
@@ -255,8 +255,8 @@ class Bundler {
   async minifyModule(
     path: string,
     code: string,
-    map: CompactRawMappings,
-  ): Promise<{code: string, map: CompactRawMappings}> {
+    map: UnknownSourceMapMappingTypes,
+  ): Promise<{code: string, map: UnknownSourceMapMappingTypes}> {
     const sourceMap = fromRawMappings([{code, source: code, map, path}]).toMap(
       undefined,
       {},
diff --git a/packages/metro/src/DeltaBundler/DeltaTransformer.js b/packages/metro/src/DeltaBundler/DeltaTransformer.js
index 9017963b..20a4ae4d 100644
--- a/packages/metro/src/DeltaBundler/DeltaTransformer.js
+++ b/packages/metro/src/DeltaBundler/DeltaTransformer.js
@@ -29,7 +29,7 @@ import type DependencyGraph from '../node-haste/DependencyGraph';
 import type Module from '../node-haste/Module';
 import type {Options as BundleOptions, MainOptions} from './';
 import type {DependencyEdges} from './traverseDependencies';
-import type {CompactRawMappings} from 'metro-source-map';
+import type {UnknownSourceMapMappingTypes} from 'metro-source-map';
 
 export type DeltaEntryType =
   | 'asset'
@@ -41,7 +41,7 @@ export type DeltaEntryType =
 export type DeltaEntry = {|
   +code: string,
   +id: number,
-  +map: CompactRawMappings,
+  +map: UnknownSourceMapMappingTypes,
   +name: string,
   +path: string,
   +source: string,
@@ -515,7 +515,7 @@ class DeltaTransformer extends EventEmitter {
   ): Promise<{
     +code: string,
     +dependencies: Array<string>,
-    +map: CompactRawMappings,
+    +map: UnknownSourceMapMappingTypes,
     +source: string,
   }> {
     return await module.read(
diff --git a/packages/metro/src/DeltaBundler/Serializers.js b/packages/metro/src/DeltaBundler/Serializers.js
index 80149863..b3c53cd7 100644
--- a/packages/metro/src/DeltaBundler/Serializers.js
+++ b/packages/metro/src/DeltaBundler/Serializers.js
@@ -28,7 +28,7 @@ import type DeltaTransformer, {
   DeltaEntry,
   DeltaTransformResponse,
 } from './DeltaTransformer';
-import type {MappingsMap} from 'metro-source-map';
+import type {BabelSourceMap} from 'babel-core';
 
 export type Options = BundleOptions & {
   deltaBundleId: ?string,
@@ -86,7 +86,7 @@ async function fullSourceMap(
 async function fullSourceMapObject(
   deltaBundler: DeltaBundler,
   options: Options,
-): Promise<MappingsMap> {
+): Promise<BabelSourceMap> {
   const {modules} = await _getAllModules(deltaBundler, options);
 
   return fromRawMappings(modules).toMap(undefined, {
diff --git a/packages/metro/src/JSTransformer/index.js b/packages/metro/src/JSTransformer/index.js
index 75856b55..c3f03454 100644
--- a/packages/metro/src/JSTransformer/index.js
+++ b/packages/metro/src/JSTransformer/index.js
@@ -17,9 +17,9 @@ const {Logger} = require('metro-core');
 const debug = require('debug')('Metro:JStransformer');
 const Worker = require('jest-worker').default;
 
+import type {BabelSourceMap} from 'babel-core';
 import type {Options, TransformedCode} from './worker';
 import type {LocalPath} from '../node-haste/lib/toLocalPath';
-import type {MappingsMap} from 'metro-source-map';
 import type {ResultWithMap} from './worker/minify';
 
 import typeof {minify as Minify, transform as Transform} from './worker';
@@ -74,7 +74,7 @@ module.exports = class Transformer {
   async minify(
     filename: string,
     code: string,
-    sourceMap: MappingsMap,
+    sourceMap: BabelSourceMap,
   ): Promise<ResultWithMap> {
     return await this._worker.minify(filename, code, sourceMap);
   }
diff --git a/packages/metro/src/JSTransformer/worker/constant-folding.js b/packages/metro/src/JSTransformer/worker/constant-folding.js
index 46597935..834e69ca 100644
--- a/packages/metro/src/JSTransformer/worker/constant-folding.js
+++ b/packages/metro/src/JSTransformer/worker/constant-folding.js
@@ -14,7 +14,8 @@
 
 const babel = require('babel-core');
 
-import type {Ast, SourceMap as MappingsMap} from 'babel-core';
+import type {Ast, BabelSourceMap} from 'babel-core';
+
 const t = babel.types;
 
 const Conditional = {
@@ -76,7 +77,7 @@ function constantFolding(
   transformResult: {
     ast: Ast,
     code?: ?string,
-    map: ?MappingsMap,
+    map: ?BabelSourceMap,
   },
 ) {
   return babel.transformFromAst(transformResult.ast, transformResult.code, {
diff --git a/packages/metro/src/JSTransformer/worker/index.js b/packages/metro/src/JSTransformer/worker/index.js
index dbdad3d9..b26c1350 100644
--- a/packages/metro/src/JSTransformer/worker/index.js
+++ b/packages/metro/src/JSTransformer/worker/index.js
@@ -27,7 +27,8 @@ const path = require('path');
 const {compactMapping} = require('metro-source-map');
 
 import type {LogEntry} from 'metro-core/src/Logger';
-import type {CompactRawMappings, MappingsMap} from 'metro-source-map';
+import type {BabelSourceMap} from 'babel-core';
+import type {UnknownSourceMapMappingTypes} from 'metro-source-map';
 import type {LocalPath} from '../../node-haste/lib/toLocalPath';
 import type {ResultWithMap} from './minify';
 import type {Ast, Plugins as BabelPlugins} from 'babel-core';
@@ -35,7 +36,7 @@ import type {Ast, Plugins as BabelPlugins} from 'babel-core';
 export type TransformedCode = {
   code: string,
   dependencies: $ReadOnlyArray<string>,
-  map: CompactRawMappings,
+  map: UnknownSourceMapMappingTypes,
 };
 
 export type TransformArgs<ExtraOptions: {}> = {|
@@ -219,7 +220,7 @@ function transformCode(
 function minifyCode(
   filename: string,
   code: string,
-  sourceMap: MappingsMap,
+  sourceMap: BabelSourceMap,
 ): ResultWithMap | Promise<ResultWithMap> {
   try {
     return minify.withSourceMap(code, sourceMap, filename);
diff --git a/packages/metro/src/JSTransformer/worker/inline.js b/packages/metro/src/JSTransformer/worker/inline.js
index f5411ac3..08408e74 100644
--- a/packages/metro/src/JSTransformer/worker/inline.js
+++ b/packages/metro/src/JSTransformer/worker/inline.js
@@ -16,7 +16,8 @@ const babel = require('babel-core');
 const inlinePlatform = require('./inline-platform');
 const invariant = require('fbjs/lib/invariant');
 
-import type {Ast, SourceMap as MappingsMap} from 'babel-core';
+import type {Ast} from 'babel-core';
+import type {BabelSourceMap} from 'babel-core';
 const t = babel.types;
 
 const env = {name: 'env'};
@@ -104,12 +105,12 @@ const plugin = () => inlinePlugin;
 type AstResult = {
   ast: Ast,
   code: ?string,
-  map: ?MappingsMap,
+  map: ?BabelSourceMap,
 };
 
 function inline(
   filename: string,
-  transformResult: {ast?: ?Ast, code: string, map: ?MappingsMap},
+  transformResult: {ast?: ?Ast, code: string, map: ?BabelSourceMap},
   options: {+dev: boolean, +platform: ?string},
 ): AstResult {
   const code = transformResult.code;
diff --git a/packages/metro/src/JSTransformer/worker/minify.js b/packages/metro/src/JSTransformer/worker/minify.js
index dc7f06dc..bc2e1b1d 100644
--- a/packages/metro/src/JSTransformer/worker/minify.js
+++ b/packages/metro/src/JSTransformer/worker/minify.js
@@ -14,11 +14,11 @@
 
 const uglify = require('uglify-es');
 
-import type {MappingsMap} from 'metro-source-map';
+import type {BabelSourceMap} from 'babel-core';
 
 export type ResultWithMap = {
   code: string,
-  map: MappingsMap,
+  map: BabelSourceMap,
 };
 
 function noSourceMap(code: string): string {
@@ -27,17 +27,17 @@ function noSourceMap(code: string): string {
 
 function withSourceMap(
   code: string,
-  sourceMap: ?MappingsMap,
+  sourceMap: ?BabelSourceMap,
   filename: string,
 ): ResultWithMap {
   const result = minify(code, sourceMap);
 
-  const map: MappingsMap = JSON.parse(result.map);
+  const map: BabelSourceMap = JSON.parse(result.map);
   map.sources = [filename];
   return {code: result.code, map};
 }
 
-function minify(inputCode: string, inputMap: ?MappingsMap) {
+function minify(inputCode: string, inputMap: ?BabelSourceMap) {
   const result = uglify.minify(inputCode, {
     mangle: {toplevel: true},
     output: {
diff --git a/packages/metro/src/ModuleGraph/types.flow.js b/packages/metro/src/ModuleGraph/types.flow.js
index 6f1ba3fd..acd1a4ba 100644
--- a/packages/metro/src/ModuleGraph/types.flow.js
+++ b/packages/metro/src/ModuleGraph/types.flow.js
@@ -12,12 +12,9 @@
 'use strict';
 
 import type {Ast} from 'babel-core';
+import type {BabelSourceMap} from 'babel-core';
 import type {Console} from 'console';
-import type {
-  FBSourceMap,
-  MappingsMap,
-  MetroSourceMap as SourceMap,
-} from 'metro-source-map';
+import type {FBSourceMap, MetroSourceMap as SourceMap} from 'metro-source-map';
 
 export type {Transformer} from '../JSTransformer/worker';
 
@@ -37,7 +34,7 @@ type Dependency = {|
 
 export type File = {|
   code: string,
-  map: ?MappingsMap,
+  map: ?BabelSourceMap,
   path: string,
   type: CodeFileTypes,
 |};
@@ -144,7 +141,7 @@ type ResolveOptions = {
 export type TransformerResult = {|
   ast: ?Ast,
   code: string,
-  map: ?MappingsMap,
+  map: ?BabelSourceMap,
 |};
 
 export type TransformResultDependency = {|
@@ -164,7 +161,7 @@ export type TransformResult = {|
   code: string,
   dependencies: $ReadOnlyArray<TransformResultDependency>,
   dependencyMapName?: string,
-  map: ?MappingsMap,
+  map: ?BabelSourceMap,
 |};
 
 export type TransformResults = {[string]: TransformResult};
diff --git a/packages/metro/src/ModuleGraph/worker/optimize-module.js b/packages/metro/src/ModuleGraph/worker/optimize-module.js
index 31adfe69..0a3283e2 100644
--- a/packages/metro/src/ModuleGraph/worker/optimize-module.js
+++ b/packages/metro/src/ModuleGraph/worker/optimize-module.js
@@ -23,7 +23,8 @@ const optimizeDependencies = require('./optimizeDependencies');
 const sourceMap = require('source-map');
 
 import type {TransformedSourceFile, TransformResult} from '../types.flow';
-import type {MappingsMap, MetroSourceMap as SourceMap} from 'metro-source-map';
+import type {BabelSourceMap} from 'babel-core';
+import type {MetroSourceMap as SourceMap} from 'metro-source-map';
 import type {PostMinifyProcess} from '../../Bundler/index.js';
 
 export type OptimizationOptions = {|
@@ -112,7 +113,7 @@ function mergeSourceMaps(
   file: string,
   originalMap: SourceMap,
   secondMap: SourceMap,
-): MappingsMap {
+): BabelSourceMap {
   const merged = new sourceMap.SourceMapGenerator();
   const inputMap = new sourceMap.SourceMapConsumer(originalMap);
   new sourceMap.SourceMapConsumer(secondMap).eachMapping(mapping => {
diff --git a/packages/metro/src/lib/TransformCaching.js b/packages/metro/src/lib/TransformCaching.js
index 71646162..ab349acd 100644
--- a/packages/metro/src/lib/TransformCaching.js
+++ b/packages/metro/src/lib/TransformCaching.js
@@ -24,7 +24,7 @@ const writeFileAtomicSync = require('write-file-atomic').sync;
 import type {Options as WorkerOptions} from '../JSTransformer/worker';
 import type {Reporter} from './reporting';
 import type {LocalPath} from '../node-haste/lib/toLocalPath';
-import type {CompactRawMappings} from 'metro-source-map';
+import type {UnknownSourceMapMappingTypes} from 'metro-source-map';
 
 type CacheFilePaths = {transformedCode: string, metadata: string};
 export type GetTransformCacheKey = (options: {}) => string;
@@ -34,7 +34,7 @@ const CACHE_SUB_DIR = 'cache';
 export type CachedResult = {
   code: string,
   dependencies: $ReadOnlyArray<string>,
-  map: CompactRawMappings,
+  map: UnknownSourceMapMappingTypes,
 };
 
 export type TransformCacheResult = ?CachedResult;
@@ -324,7 +324,7 @@ function readMetadataFileSync(
   cachedResultHash: string,
   cachedSourceHash: string,
   dependencies: Array<string>,
-  sourceMap: CompactRawMappings,
+  sourceMap: UnknownSourceMapMappingTypes,
 } {
   const metadataStr = fs.readFileSync(metadataFilePath, 'utf8');
   const metadata = tryParseJSON(metadataStr);
diff --git a/packages/metro/src/node-haste/Module.js b/packages/metro/src/node-haste/Module.js
index d4cef73d..b4c5c3a8 100644
--- a/packages/metro/src/node-haste/Module.js
+++ b/packages/metro/src/node-haste/Module.js
@@ -35,12 +35,12 @@ import type {Reporter} from '../lib/reporting';
 import type DependencyGraphHelpers from './DependencyGraph/DependencyGraphHelpers';
 import type ModuleCache from './ModuleCache';
 import type {LocalPath} from './lib/toLocalPath';
-import type {CompactRawMappings} from 'metro-source-map';
+import type {UnknownSourceMapMappingTypes} from 'metro-source-map';
 
 export type ReadResult = {
   +code: string,
   +dependencies: $ReadOnlyArray<string>,
-  +map: CompactRawMappings,
+  +map: UnknownSourceMapMappingTypes,
   +source: string,
 };
 
diff --git a/packages/metro/src/shared/output/unbundle/util.js b/packages/metro/src/shared/output/unbundle/util.js
index 09fea30b..6bf8111c 100644
--- a/packages/metro/src/shared/output/unbundle/util.js
+++ b/packages/metro/src/shared/output/unbundle/util.js
@@ -15,10 +15,10 @@ 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,
-  MappingsMap,
   MetroSourceMap as SourceMap,
 } from 'metro-source-map';
 
@@ -29,7 +29,7 @@ const countLines = (string: string) => (string.match(newline) || []).length + 1;
 function lineToLineSourceMap(
   source: string,
   filename: string = '',
-): MappingsMap {
+): BabelSourceMap {
   // The first line mapping in our package is the base64vlq code for zeros (A).
   const firstLine = 'AAAA;';