diff --git a/lib/arborist/build-ideal-tree.js b/lib/arborist/build-ideal-tree.js
index 94647727b..08a6e0585 100644
--- a/lib/arborist/build-ideal-tree.js
+++ b/lib/arborist/build-ideal-tree.js
@@ -110,6 +110,10 @@ module.exports = cls => class IdealTreeBuilder extends Tracker(Virtual(Actual(cl
     this[_manifests] = new Map()
   }
 
+  get explicitRequests () {
+    return new Set(this[_explicitRequests])
+  }
+
   // public method
   buildIdealTree (options = {}) {
     if (this.idealTree)
diff --git a/lib/arborist/reify.js b/lib/arborist/reify.js
index bb0a11baf..fe82f83d1 100644
--- a/lib/arborist/reify.js
+++ b/lib/arborist/reify.js
@@ -35,7 +35,6 @@ const promiseCallLimit = require('promise-call-limit')
 const Ideal = require('./build-ideal-tree.js')
 const optionalSet = require('../optional-set.js')
 
-const _diff = Symbol('diff')
 const _retiredPaths = Symbol('retiredPaths')
 const _retiredUnchanged = Symbol('retiredUnchanged')
 const _sparseTreeDirs = Symbol('sparseTreeDirs')
@@ -109,7 +108,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
     this[_scriptShell] = scriptShell
     this[_savePrefix] = savePrefix
 
-    this[_diff] = null
+    this.diff = null
     this[_retiredPaths] = {}
     this[_retiredUnchanged] = {}
     this[_sparseTreeDirs] = new Set()
@@ -169,11 +168,11 @@ module.exports = cls => class Reifier extends Ideal(cls) {
 
     // find all the nodes that need to change between the actual
     // and ideal trees.
-    this[_diff] = Diff.calculate({
+    this.diff = Diff.calculate({
       actual: this.actualTree,
       ideal: this.idealTree,
     })
-    for (const node of this[_diff].removed) {
+    for (const node of this.diff.removed) {
       this[_addNodeToTrashList](node)
     }
   }
@@ -199,7 +198,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
   // changed or removed, so that we can rollback if necessary.
   [_retireShallowNodes] () {
     const moves = this[_retiredPaths] = {}
-    for (const diff of this[_diff].children) {
+    for (const diff of this.diff.children) {
       if (diff.action === 'CHANGE' || diff.action === 'REMOVE') {
         // we'll have to clean these up at the end, so add them to the list
         this[_addNodeToTrashList](diff.actual, true)
@@ -259,7 +258,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
   [_createSparseTree] () {
     // if we call this fn again, we look for the previous list
     // so that we can avoid making the same directory multiple times
-    const dirs = this[_diff].leaves
+    const dirs = this.diff.leaves
       .filter(diff => {
         return (diff.action === 'ADD' || diff.action === 'CHANGE') &&
           !this[_sparseTreeDirs].has(diff.ideal.path)
@@ -289,7 +288,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
   // we need to unpack them, read that shrinkwrap file, and then update
   // the tree by calling loadVirtual with the node as the root.
   [_loadShrinkwrapsAndUpdateTrees] (seen = new Set()) {
-    const shrinkwraps = this[_diff].leaves
+    const shrinkwraps = this.diff.leaves
       .filter(d => (d.action === 'CHANGE' || d.action === 'ADD') &&
         d.ideal.hasShrinkwrap && !seen.has(d.ideal) &&
         !this[_trashList].has(d.ideal.path))
@@ -498,7 +497,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
     const bundlesByDepth = new Map()
     let maxBundleDepth = -1
     dfwalk({
-      tree: this[_diff],
+      tree: this.diff,
       visit: diff => {
         const node = diff.ideal
         if (node && !node.isRoot && node.package.bundleDependencies &&
@@ -524,7 +523,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
   [_unpackNewModules] () {
     const unpacks = []
     dfwalk({
-      tree: this[_diff],
+      tree: this.diff,
       filter: diff => diff.ideal,
       visit: diff => {
         const node = diff.ideal
@@ -555,7 +554,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
     // shallowest nodes that we moved aside in the first place.
     const moves = this[_retiredPaths]
     this[_retiredUnchanged] = {}
-    return promiseAllRejectLate(this[_diff].children.map(diff => {
+    return promiseAllRejectLate(this.diff.children.map(diff => {
       const realFolder = (diff.actual || diff.ideal).path
       const retireFolder = moves[realFolder]
       this[_retiredUnchanged][retireFolder] = []
@@ -620,7 +619,7 @@ module.exports = cls => class Reifier extends Ideal(cls) {
     // deps before attempting to build it itself
     const installedNodes = []
     dfwalk({
-      tree: this[_diff],
+      tree: this.diff,
       leave: diff => installedNodes.push(diff.ideal),
       // process adds before changes, ignore removals
       getChildren: diff => diff && diff.children,
diff --git a/test/arborist/build-ideal-tree.js b/test/arborist/build-ideal-tree.js
index 9c80eb297..82460203e 100644
--- a/test/arborist/build-ideal-tree.js
+++ b/test/arborist/build-ideal-tree.js
@@ -205,6 +205,16 @@ t.test('dedupe example - deduped', t => {
   return t.resolveMatchSnapshot(printIdeal(path), 'dedupe testing')
 })
 
+t.test('expose explicitRequest', async t => {
+  const path = resolve(__dirname, '../fixtures/simple')
+  const arb = new Arborist({ path })
+  const tree = await arb.buildIdealTree({ add: [ 'abbrev' ] })
+  t.ok(arb.explicitRequests, 'exposes the explicit request')
+  t.strictSame(arb.explicitRequests, new Set(['abbrev']))
+  t.ok(arb.explicitRequests.has('abbrev'), 'should contain explicit item')
+  t.end()
+})
+
 t.test('bundle deps example 1', t => {
   // NB: this results in ignoring the bundled deps when building the
   // ideal tree.  When we reify, we'll have to ignore the deps that
diff --git a/test/arborist/reify.js b/test/arborist/reify.js
index 8c642a422..e3783953a 100644
--- a/test/arborist/reify.js
+++ b/test/arborist/reify.js
@@ -200,7 +200,9 @@ t.test('update a bundling node without updating all of its deps', t => {
 t.test('omit optional dep', t => {
   const path = fixture(t, 'tap-react15-collision-legacy-sw')
   const ignoreScripts = true
-  return new Arborist({ path, ignoreScripts }).reify({ omit: ['optional'] })
+
+  const arb = new Arborist({ path, ignoreScripts })
+  return arb.reify({ omit: ['optional'] })
     .then(tree => {
       t.equal(tree.children.get('fsevents'), undefined, 'no fsevents in tree')
       t.throws(() => fs.statSync(path + '/node_modules/fsevents'), 'no fsevents unpacked')
@@ -209,6 +211,7 @@ t.test('omit optional dep', t => {
         optional: true,
       }, 'fsevents present in lockfile')
     })
+    .then(() => t.ok(arb.diff, 'has a diff tree'))
 })
 
 t.test('dev, optional, devOptional flags and omissions', t => {
diff --git a/test/fixtures/simple/package.json b/test/fixtures/simple/package.json
new file mode 100644
index 000000000..7a8fc947f
--- /dev/null
+++ b/test/fixtures/simple/package.json
@@ -0,0 +1,4 @@
+{
+  "name": "simple",
+  "version": "2.0.0" 
+}