diff --git a/packages/metro-source-map/src/source-map.js b/packages/metro-source-map/src/source-map.js
index eb0e2623..352b9078 100644
--- a/packages/metro-source-map/src/source-map.js
+++ b/packages/metro-source-map/src/source-map.js
@@ -17,9 +17,6 @@ const SourceMap = require('source-map');
 
 import type {BabelSourceMap} from 'babel-core';
 import type {BabelSourceMapSegment} from 'babel-generator';
-import type {RawMapping as UnknownSourceMapMappingType} from 'source-map';
-
-export type UnknownSourceMapMappingTypes = Array<UnknownSourceMapMappingType>;
 
 type GeneratedCodeMapping = [number, number];
 type SourceMapping = [number, number, number, number];
diff --git a/packages/metro/src/Bundler/index.js b/packages/metro/src/Bundler/index.js
index 622a2148..4b7c56ef 100644
--- a/packages/metro/src/Bundler/index.js
+++ b/packages/metro/src/Bundler/index.js
@@ -34,7 +34,7 @@ import type {Reporter} from '../lib/reporting';
 import type {HasteImpl} from '../node-haste/Module';
 import type {BabelSourceMap} from 'babel-core';
 import type {
-  UnknownSourceMapMappingTypes,
+  MetroSourceMapSegmentTuple,
   MetroSourceMap as SourceMap,
 } from 'metro-source-map';
 
@@ -255,8 +255,8 @@ class Bundler {
   async minifyModule(
     path: string,
     code: string,
-    map: UnknownSourceMapMappingTypes,
-  ): Promise<{code: string, map: UnknownSourceMapMappingTypes}> {
+    map: Array<MetroSourceMapSegmentTuple>,
+  ): Promise<{code: string, map: Array<MetroSourceMapSegmentTuple>}> {
     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 020a6527..5e30ee5f 100644
--- a/packages/metro/src/DeltaBundler/DeltaTransformer.js
+++ b/packages/metro/src/DeltaBundler/DeltaTransformer.js
@@ -30,7 +30,7 @@ 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 {UnknownSourceMapMappingTypes} from 'metro-source-map';
+import type {MetroSourceMapSegmentTuple} from 'metro-source-map';
 
 export type DeltaEntryType =
   | 'asset'
@@ -42,7 +42,7 @@ export type DeltaEntryType =
 export type DeltaEntry = {|
   +code: string,
   +id: number,
-  +map: UnknownSourceMapMappingTypes,
+  +map: Array<MetroSourceMapSegmentTuple>,
   +name: string,
   +path: string,
   +source: string,
@@ -530,7 +530,7 @@ class DeltaTransformer extends EventEmitter {
   ): Promise<{
     +code: string,
     +dependencies: Array<string>,
-    +map: UnknownSourceMapMappingTypes,
+    +map: Array<MetroSourceMapSegmentTuple>,
     +source: string,
   }> {
     return await module.read(
diff --git a/packages/metro/src/JSTransformer/worker/index.js b/packages/metro/src/JSTransformer/worker/index.js
index d2e657a7..aacffcc5 100644
--- a/packages/metro/src/JSTransformer/worker/index.js
+++ b/packages/metro/src/JSTransformer/worker/index.js
@@ -28,7 +28,7 @@ const {toSegmentTuple} = require('metro-source-map');
 
 import type {LogEntry} from 'metro-core/src/Logger';
 import type {BabelSourceMap} from 'babel-core';
-import type {UnknownSourceMapMappingTypes} from 'metro-source-map';
+import type {MetroSourceMapSegmentTuple} 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';
@@ -36,7 +36,7 @@ import type {Ast, Plugins as BabelPlugins} from 'babel-core';
 export type TransformedCode = {
   code: string,
   dependencies: $ReadOnlyArray<string>,
-  map: UnknownSourceMapMappingTypes,
+  map: Array<MetroSourceMapSegmentTuple>,
 };
 
 export type TransformArgs<ExtraOptions: {}> = {|
diff --git a/packages/metro/src/lib/TransformCaching.js b/packages/metro/src/lib/TransformCaching.js
index ab349acd..54672caa 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 {UnknownSourceMapMappingTypes} from 'metro-source-map';
+import type {MetroSourceMapSegmentTuple} 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: UnknownSourceMapMappingTypes,
+  map: Array<MetroSourceMapSegmentTuple>,
 };
 
 export type TransformCacheResult = ?CachedResult;
@@ -324,7 +324,7 @@ function readMetadataFileSync(
   cachedResultHash: string,
   cachedSourceHash: string,
   dependencies: Array<string>,
-  sourceMap: UnknownSourceMapMappingTypes,
+  sourceMap: Array<MetroSourceMapSegmentTuple>,
 } {
   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 b4c5c3a8..c276d712 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 {UnknownSourceMapMappingTypes} from 'metro-source-map';
+import type {MetroSourceMapSegmentTuple} from 'metro-source-map';
 
 export type ReadResult = {
   +code: string,
   +dependencies: $ReadOnlyArray<string>,
-  +map: UnknownSourceMapMappingTypes,
+  +map: Array<MetroSourceMapSegmentTuple>,
   +source: string,
 };