diff --git a/src/render/glyph_manager.js b/src/render/glyph_manager.js
index ad13298e4e4..c65c7490759 100644
--- a/src/render/glyph_manager.js
+++ b/src/render/glyph_manager.js
@@ -8,6 +8,7 @@ const {AlphaImage} = require('../util/image');
 
 import type {StyleGlyph} from '../style/style_glyph';
 import type {RequestTransformFunction} from '../ui/map';
+import type {Callback} from '../types/callback';
 
 type Entry = {
     // null means we've requested the range, but the glyph wasn't included in the result.
diff --git a/src/render/image_manager.js b/src/render/image_manager.js
index 252b5632251..c5fbd954ca8 100644
--- a/src/render/image_manager.js
+++ b/src/render/image_manager.js
@@ -9,6 +9,7 @@ const assert = require('assert');
 import type {StyleImage} from '../style/style_image';
 import type {ImagePosition} from './image_atlas';
 import type {Bin} from '@mapbox/shelf-pack';
+import type {Callback} from '../types/callback';
 
 type Pattern = {
     bin: Bin,
diff --git a/src/source/geojson_source.js b/src/source/geojson_source.js
index 8497ac7ed21..a20c993cf47 100644
--- a/src/source/geojson_source.js
+++ b/src/source/geojson_source.js
@@ -11,6 +11,7 @@ import type {Source} from './source';
 import type Map from '../ui/map';
 import type Dispatcher from '../util/dispatcher';
 import type Tile from './tile';
+import type {Callback} from '../types/callback';
 
 /**
  * A source containing GeoJSON.
diff --git a/src/source/geojson_worker_source.js b/src/source/geojson_worker_source.js
index 90486dc1763..0328fad60a1 100644
--- a/src/source/geojson_worker_source.js
+++ b/src/source/geojson_worker_source.js
@@ -19,6 +19,7 @@ import type StyleLayerIndex from '../style/style_layer_index';
 
 import type {LoadVectorDataCallback} from './vector_tile_worker_source';
 import type {RequestParameters} from '../util/ajax';
+import type { Callback } from '../types/callback';
 
 export type GeoJSON = Object;
 
diff --git a/src/source/image_source.js b/src/source/image_source.js
index a7c9e8a41fd..1a7a4a3b38e 100644
--- a/src/source/image_source.js
+++ b/src/source/image_source.js
@@ -19,6 +19,7 @@ import type Map from '../ui/map';
 import type Dispatcher from '../util/dispatcher';
 import type Tile from './tile';
 import type Coordinate from '../geo/coordinate';
+import type {Callback} from '../types/callback';
 
 export type ImageTextureSource =
   ImageData |
diff --git a/src/source/load_tilejson.js b/src/source/load_tilejson.js
index e49e228e4d3..5b9f4d9bec6 100644
--- a/src/source/load_tilejson.js
+++ b/src/source/load_tilejson.js
@@ -6,6 +6,7 @@ const browser = require('../util/browser');
 const normalizeURL = require('../util/mapbox').normalizeSourceURL;
 
 import type {RequestTransformFunction} from '../ui/map';
+import type {Callback} from '../types/callback';
 
 module.exports = function(options: any, requestTransformFn: RequestTransformFunction, callback: Callback<TileJSON>) {
     const loaded = function(err, tileJSON: any) {
diff --git a/src/source/raster_tile_source.js b/src/source/raster_tile_source.js
index ef93dbccad9..431367380e2 100644
--- a/src/source/raster_tile_source.js
+++ b/src/source/raster_tile_source.js
@@ -13,6 +13,7 @@ import type TileCoord from './tile_coord';
 import type Map from '../ui/map';
 import type Dispatcher from '../util/dispatcher';
 import type Tile from './tile';
+import type {Callback} from '../types/callback';
 
 class RasterTileSource extends Evented implements Source {
     type: 'raster';
diff --git a/src/source/source.js b/src/source/source.js
index be8d46330bf..28669696936 100644
--- a/src/source/source.js
+++ b/src/source/source.js
@@ -7,6 +7,7 @@ import type Evented from '../util/evented';
 import type Map from '../ui/map';
 import type Tile from './tile';
 import type TileCoord from './tile_coord';
+import type {Callback} from '../types/callback';
 
 /**
  * The `Source` interface must be implemented by each source type, including "core" types (`vector`, `raster`,
diff --git a/src/source/source_cache.js b/src/source/source_cache.js
index 729d35345b4..1e55d4d8cb3 100644
--- a/src/source/source_cache.js
+++ b/src/source/source_cache.js
@@ -17,6 +17,7 @@ import type Dispatcher from '../util/dispatcher';
 import type Transform from '../geo/transform';
 import type {TileState} from './tile';
 import type CollisionIndex from '../symbol/collision_index';
+import type {Callback} from '../types/callback';
 
 /**
  * `SourceCache` is responsible for
diff --git a/src/source/vector_tile_source.js b/src/source/vector_tile_source.js
index 1bc9d148bb4..5568043c350 100644
--- a/src/source/vector_tile_source.js
+++ b/src/source/vector_tile_source.js
@@ -13,6 +13,7 @@ import type TileCoord from './tile_coord';
 import type Map from '../ui/map';
 import type Dispatcher from '../util/dispatcher';
 import type Tile from './tile';
+import type {Callback} from '../types/callback';
 
 class VectorTileSource extends Evented implements Source {
     type: 'vector';
diff --git a/src/source/vector_tile_worker_source.js b/src/source/vector_tile_worker_source.js
index 6a07d0a9125..bc21ccdd15b 100644
--- a/src/source/vector_tile_worker_source.js
+++ b/src/source/vector_tile_worker_source.js
@@ -15,6 +15,7 @@ import type {
 
 import type Actor from '../util/actor';
 import type StyleLayerIndex from '../style/style_layer_index';
+import type {Callback} from '../types/callback';
 
 export type LoadVectorTileResult = {
     vectorTile: VectorTile;
diff --git a/src/source/worker.js b/src/source/worker.js
index a5ed9400f9b..aff8c64e8be 100644
--- a/src/source/worker.js
+++ b/src/source/worker.js
@@ -17,6 +17,7 @@ import type {
 } from '../source/worker_source';
 
 import type {WorkerGlobalScopeInterface} from '../util/web_worker';
+import type {Callback} from '../types/callback';
 
 /**
  * @private
diff --git a/src/style/load_glyph_range.js b/src/style/load_glyph_range.js
index e9eb5169f16..6dcef00459c 100644
--- a/src/style/load_glyph_range.js
+++ b/src/style/load_glyph_range.js
@@ -6,6 +6,7 @@ const parseGlyphPBF = require('./parse_glyph_pbf');
 
 import type {StyleGlyph} from './style_glyph';
 import type {RequestTransformFunction} from '../ui/map';
+import type {Callback} from '../types/callback';
 
 module.exports = function (fontstack: string,
                            range: number,
diff --git a/src/style/load_sprite.js b/src/style/load_sprite.js
index 473d836aee6..6f6bdfee91b 100644
--- a/src/style/load_sprite.js
+++ b/src/style/load_sprite.js
@@ -7,6 +7,7 @@ const {RGBAImage} = require('../util/image');
 
 import type {StyleImage} from './style_image';
 import type {RequestTransformFunction} from '../ui/map';
+import type {Callback} from '../types/callback';
 
 module.exports = function(baseURL: string,
                           transformRequestCallback: RequestTransformFunction,
diff --git a/src/style/style.js b/src/style/style.js
index c6aa53f66e4..6ee38275f6e 100644
--- a/src/style/style.js
+++ b/src/style/style.js
@@ -33,6 +33,7 @@ import type {Source} from '../source/source';
 import type {StyleImage} from './style_image';
 import type {StyleGlyph} from './style_glyph';
 import type CollisionIndex from '../symbol/collision_index';
+import type {Callback} from '../types/callback';
 
 const supportedDiffOperations = util.pick(diff.operations, [
     'addLayer',
diff --git a/flow-typed/callback.js b/src/types/callback.js
similarity index 87%
rename from flow-typed/callback.js
rename to src/types/callback.js
index de55bcd014c..1c5416c00fc 100644
--- a/flow-typed/callback.js
+++ b/src/types/callback.js
@@ -1,3 +1,4 @@
+// @flow
 
 // Flow can't perfectly type Node-style callbacks yet; it does not have a way to
 // express that if the first parameter is null, the second is not, so for the time
@@ -13,5 +14,4 @@
 //    });
 //
 // See https://github.com/facebook/flow/issues/2123 for more.
-
-declare type Callback<T> = (error: ?Error, result: ?T) => void;
+export type Callback<T> = (error: ?Error, result: ?T) => void;
diff --git a/src/util/ajax.js b/src/util/ajax.js
index 5d97c29936e..94dec7bdf01 100644
--- a/src/util/ajax.js
+++ b/src/util/ajax.js
@@ -2,6 +2,8 @@
 
 const window = require('./window');
 
+import type { Callback } from '../types/callback';
+
 /**
  * The type of a resource.
  * @private
diff --git a/src/util/util.js b/src/util/util.js
index 540e65f43d2..2236d92255f 100644
--- a/src/util/util.js
+++ b/src/util/util.js
@@ -4,6 +4,8 @@ const UnitBezier = require('@mapbox/unitbezier');
 const Coordinate = require('../geo/coordinate');
 const Point = require('@mapbox/point-geometry');
 
+import type {Callback} from '../types/callback';
+
 /**
  * @module util
  * @private