diff --git a/lib/node-labels.js b/lib/node-labels.js
index fb1e7698..9874754a 100644
--- a/lib/node-labels.js
+++ b/lib/node-labels.js
@@ -9,24 +9,49 @@ const subSystemLabelsMap = new Map([
   [/^([A-Z]+$|CODE_OF_CONDUCT|ROADMAP|WORKING_GROUPS|GOVERNANCE|CHANGELOG|\.mail|\.git.+)/, 'meta'],
   // things that edit top-level .md files are always a doc change
   [/^\w+\.md$/, 'doc'],
+
+  /* Dependencies */
   // libuv needs an explicit mapping, as the ordinary /deps/ mapping below would
   // end up as libuv changes labeled with "uv" (which is a non-existing label)
   [/^deps\/uv\//, 'libuv'],
-  [/^deps\/([^/]+)/, '$1']
+  [/^deps\/([^/]+)/, '$1'],
+
+  /* JS subsystems */
+  // Oddities first
+  [/^lib\/(punycode|\w+\/freelist|sys\.js)/, ''], // TODO: ignore better?
+  [/^lib\/string_decoder/, 'buffer'],
+  [/^lib\/constants\.js$/, 'lib / src'],
+  [/^lib\/_(debug_agent|debugger)\.js$/, 'debugger'],
+  [/^lib(\/\w+)?\/(_)?link(ed)?list/, 'timers'],
+  [/^lib\/\w+\/bootstrap_node/, 'lib / src'],
+  [/^lib\/\w+\/v8_prof_/, 'tools'],
+  [/^lib\/\w+\/socket_list/, 'net'],
+  [/^lib\/\w+\/streams$/, 'stream'],
+  // All other lib/ files map directly
+  [/^lib\/_(\w+)_\w+\.js?$/, '$1'], // e.g. _(stream)_wrap
+  [/^lib(\/internal)?\/(\w+)\.js?$/, '$2'], // other .js files
+  [/^lib\/internal\/(\w+)$/, '$1'] // internal subfolders
 ])
 
+const jsSubsystemList = [
+  'debugger', 'assert', 'buffer', 'child_process', 'cluster', 'console',
+  'crypto', 'dgram', 'dns', 'domain', 'events', 'fs', 'http', 'https', 'module',
+  'net', 'os', 'path', 'process', 'querystring', 'readline', 'repl', 'stream',
+  'timers', 'tls', 'tty', 'url', 'util', 'v8', 'vm', 'zlib'
+]
+
 const exclusiveLabelsMap = new Map([
   [/^test\//, 'test'],
   [/^doc\//, 'doc'],
   [/^benchmark\//, 'benchmark']
 ])
 
-function resolveLabels (filepathsChanged) {
+function resolveLabels (filepathsChanged, limitLib = true) {
   const exclusiveLabels = matchExclusiveSubSystem(filepathsChanged)
 
   return (exclusiveLabels.length > 0)
           ? exclusiveLabels
-          : matchAllSubSystem(filepathsChanged)
+          : matchAllSubSystem(filepathsChanged, limitLib)
 }
 
 function matchExclusiveSubSystem (filepathsChanged) {
@@ -35,19 +60,37 @@ function matchExclusiveSubSystem (filepathsChanged) {
   return (isExclusive && labels.length === 1) ? labels : []
 }
 
-function matchAllSubSystem (filepathsChanged) {
-  return matchSubSystemsByRegex(subSystemLabelsMap, filepathsChanged)
+function matchAllSubSystem (filepathsChanged, limitLib) {
+  return matchSubSystemsByRegex(
+      subSystemLabelsMap, filepathsChanged, limitLib)
 }
 
-function matchSubSystemsByRegex (rxLabelsMap, filepathsChanged) {
+function matchSubSystemsByRegex (rxLabelsMap, filepathsChanged, limitLib) {
+  const jsLabelCount = []
   // by putting matched labels into a map, we avoid duplicate labels
   const labelsMap = filepathsChanged.reduce((map, filepath) => {
     const mappedSubSystem = mappedSubSystemForFile(rxLabelsMap, filepath)
 
-    if (mappedSubSystem) {
-      map[mappedSubSystem] = true
+    if (!mappedSubSystem) {
+      // short-circuit
+      return map
     }
 
+    if (limitLib && jsSubsystemList.includes(mappedSubSystem)) {
+      if (jsLabelCount.length >= 4) {
+        for (const jsLabel of jsLabelCount) {
+          delete map[jsLabel]
+        }
+        map['lib / src'] = true
+        // short-circuit
+        return map
+      } else {
+        jsLabelCount.push(mappedSubSystem)
+      }
+    }
+
+    map[mappedSubSystem] = true
+
     return map
   }, {})
 
diff --git a/test/node-js-subsystem-labels.test.js b/test/node-js-subsystem-labels.test.js
new file mode 100644
index 00000000..1640c1e1
--- /dev/null
+++ b/test/node-js-subsystem-labels.test.js
@@ -0,0 +1,133 @@
+'use strict'
+
+const tap = require('tap')
+
+const nodeLabels = require('../lib/node-labels')
+
+tap.test('label: lib oddities', (t) => {
+  const libFiles = [
+    'lib/_debug_agent.js',
+    'lib/_http_agent.js',
+    'lib/_http_client.js',
+    'lib/_http_common.js',
+    'lib/_http_incoming.js',
+    'lib/_http_outgoing.js',
+    'lib/_http_server.js',
+    'lib/_linklist.js',
+    'lib/_stream_duplex.js',
+    'lib/_stream_passthrough.js',
+    'lib/_stream_readable.js',
+    'lib/_stream_transform.js',
+    'lib/_stream_wrap.js',
+    'lib/_stream_writable.js',
+    'lib/_tls_common.js',
+    'lib/_tls_legacy.js',
+    'lib/_tls_wrap.js',
+    'lib/constants.js',
+    'lib/punycode.js', // ignored
+    'lib/string_decoder.js',
+    'lib/sys.js', // ignored
+    'lib/internal/freelist.js', // ignored
+    'lib/internal/process',
+    'lib/internal/readme.md', // ignored
+    'lib/internal/socket_list.js',
+    'lib/internal/v8_prof_polyfill.js',
+    'lib/internal/v8_prof_processor.js'
+  ]
+
+  const labels = nodeLabels.resolveLabels(libFiles, false)
+
+  t.same(labels, [
+    'debugger',  // _debug_agent
+    'http',      // _http_*
+    'timers',    // linklist
+    'stream',    // _stream_*
+    'tls',       // _tls_*
+    'lib / src', // constants
+    'buffer',    // string_decoder
+    'process',   // internal/process/
+    'net',       // socket_list
+    'tools'      // v8_prof_*
+  ])
+
+  t.end()
+})
+
+tap.test('label: lib internals oddities duplicates', (t) => {
+  const libFiles = [
+    'lib/internal/bootstrap_node.js',
+    'lib/internal/linkedlist.js',
+    'lib/internal/streams'
+  ]
+
+  const labels = nodeLabels.resolveLabels(libFiles)
+
+  t.same(labels, [
+    'lib / src', // bootstrap_node
+    'timers',    // linkedlist
+    'stream'     // internal/streams/
+  ])
+
+  t.end()
+})
+
+tap.test('label: lib normal without "lib / src" limiting', (t) => {
+  const libFiles = [
+    'lib/_debugger.js',
+    'lib/assert.js',
+    'lib/buffer.js',
+    'lib/child_process.js',
+    'lib/cluster.js',
+    'lib/console.js',
+    'lib/crypto.js',
+    'lib/dgram.js',
+    'lib/dns.js',
+    'lib/domain.js',
+    'lib/events.js',
+    'lib/fs.js',
+    'lib/http.js',
+    'lib/https.js',
+    'lib/module.js',
+    'lib/net.js',
+    'lib/os.js',
+    'lib/path.js',
+    'lib/process.js',
+    'lib/querystring.js',
+    'lib/readline.js',
+    'lib/repl.js',
+    'lib/stream.js',
+    'lib/timers.js',
+    'lib/tls.js',
+    'lib/tty.js',
+    'lib/url.js',
+    'lib/util.js',
+    'lib/v8.js',
+    'lib/vm.js',
+    'lib/zlib.js'
+  ]
+
+  const labels = nodeLabels.resolveLabels(libFiles, false)
+
+  t.same(labels, libFiles.map((path) => /lib\/(_)?(\w+)\.js/.exec(path)[2]))
+
+  t.end()
+})
+
+tap.test('label: lib internals without "lib / src" limiting', (t) => {
+  const libFiles = [
+    'lib/internal/child_process.js',
+    'lib/internal/cluster.js',
+    'lib/internal/module.js',
+    'lib/internal/net.js',
+    'lib/internal/process.js',
+    'lib/internal/readline.js',
+    'lib/internal/repl.js',
+    'lib/internal/util.js'
+  ]
+
+  const labels = nodeLabels.resolveLabels(libFiles, false)
+
+  t.same(labels, libFiles.map((path) => /lib\/internal\/(\w+)\.js/.exec(path)[1]))
+
+  t.end()
+})
diff --git a/test/node-labels.test.js b/test/node-labels.test.js
index 792e011c..88259d19 100644
--- a/test/node-labels.test.js
+++ b/test/node-labels.test.js
@@ -32,7 +32,7 @@ tap.test('no labels: when ./test/ and ./doc/ files has been changed', (t) => {
 // https://github.com/nodejs/node/pull/6448
 tap.test('no labels: when ./test/ and ./lib/ files has been changed', (t) => {
   const labels = nodeLabels.resolveLabels([
-    'lib/assert.js',
+    'lib/punycode.js',
     'test/parallel/test-assert.js'
   ])
 
@@ -128,22 +128,34 @@ tap.test('label: "repl" when ./lib/repl.js has been changed', (t) => {
     'test/debugger/test-debugger-repl-term.js'
   ])
 
-  t.same(labels, ['repl'], { todo: true })
+  t.same(labels, ['repl'])
 
   t.end()
 })
 
-tap.test('label: "lib / src" when more than 5 sub-systems has been changed', (t) => {
+tap.test('label: "lib / src" when 5 or more JS sub-systems have been changed', (t) => {
   const labels = nodeLabels.resolveLabels([
     'lib/assert.js',
     'lib/dns.js',
     'lib/repl.js',
     'lib/process.js',
-    'src/async-wrap.cc',
     'lib/module.js'
   ])
 
-  t.same(labels, ['lib / src'], { todo: true })
+  t.same(labels, ['lib / src'])
+
+  t.end()
+})
+
+tap.test('label: "JS sub-systems when less than 5 sub-systems have changed', (t) => {
+  const labels = nodeLabels.resolveLabels([
+    'lib/assert.js',
+    'lib/dns.js',
+    'lib/repl.js',
+    'lib/process.js'
+  ])
+
+  t.same(labels, ['assert', 'dns', 'repl', 'process'])
 
   t.end()
 })