diff --git a/busted/context.lua b/busted/context.lua
index a93a903a..6596302a 100644
--- a/busted/context.lua
+++ b/busted/context.lua
@@ -23,9 +23,9 @@ local function restore(state)
       rawset(_G, k, v)
     end
   end
-  for k,_ in pairs(package.loaded) do
-    package.loaded[k] = state.loaded[k]
-  end
+  local set = function(k) package.loaded[k] = state.loaded[k] end
+  for k,_ in pairs(package.loaded) do set(k) end
+  for k,_ in pairs(state.loaded) do set(k) end
 end
 
 return function()
diff --git a/busted/core.lua b/busted/core.lua
index aa61cb66..9c304fda 100644
--- a/busted/core.lua
+++ b/busted/core.lua
@@ -1,9 +1,19 @@
+local busted_internal_loaded = {}
+
+local busted_require = function (path)
+  local default_loaded = package.loaded
+  package.loaded = busted_internal_loaded
+  local pack = require(path)
+  package.loaded = default_loaded
+  return pack
+end
+
 local getfenv = require 'busted.compatibility'.getfenv
 local setfenv = require 'busted.compatibility'.setfenv
 local unpack = require 'busted.compatibility'.unpack
-local path = require 'pl.path'
-local pretty = require 'pl.pretty'
-local system = require 'system'
+local path = busted_require 'pl.path'
+local pretty = busted_require 'pl.pretty'
+local system = busted_require 'system'
 local throw = error
 
 local failureMt = {
@@ -42,11 +52,13 @@ local function isCallable(obj)
 end
 
 return function()
-  local mediator = require 'mediator'()
-
   local busted = {}
   busted.version = '2.2.0'
 
+  busted.require = busted_require
+
+  local mediator = busted.require 'mediator'()
+
   local root = require 'busted.context'()
   busted.context = root.ref()
 
diff --git a/busted/init.lua b/busted/init.lua
index 01d6d4a5..0d368128 100644
--- a/busted/init.lua
+++ b/busted/init.lua
@@ -87,11 +87,11 @@ local function init(busted)
 
   busted.hide('file')
 
-  local assert = require 'luassert'
-  local spy    = require 'luassert.spy'
-  local mock   = require 'luassert.mock'
-  local stub   = require 'luassert.stub'
-  local match  = require 'luassert.match'
+  local assert = busted.require 'luassert'
+  local spy    = busted.require 'luassert.spy'
+  local mock   = busted.require 'luassert.mock'
+  local stub   = busted.require 'luassert.stub'
+  local match  = busted.require 'luassert.match'
 
   require 'busted.fixtures'  -- just load into the environment, not exposing it
 
diff --git a/busted/runner.lua b/busted/runner.lua
index ad8257af..ac8b9eb4 100644
--- a/busted/runner.lua
+++ b/busted/runner.lua
@@ -1,8 +1,5 @@
 -- Busted command-line runner
 
-local path = require 'pl.path'
-local tablex = require 'pl.tablex'
-local term = require 'term'
 local utils = require 'busted.utils'
 local exit = require 'busted.compatibility'.exit
 local loadstring = require 'busted.compatibility'.loadstring
@@ -11,12 +8,16 @@ local loaded = false
 return function(options)
   if loaded then return function() end else loaded = true end
 
+  local busted = require 'busted.core'()
+
+  local path = busted.require 'pl.path'
+  local tablex = busted.require 'pl.tablex'
+  local term = busted.require 'term'
+
   local isatty = io.type(io.stdout) == 'file' and term.isatty(io.stdout)
   options = tablex.update(require 'busted.options', options or {})
   options.output = options.output or (isatty and 'utfTerminal' or 'plainTerminal')
 
-  local busted = require 'busted.core'()
-
   local cli = require 'busted.modules.cli'(options)
   local filterLoader = require 'busted.modules.filter_loader'()
   local helperLoader = require 'busted.modules.helper_loader'()
diff --git a/spec/insulate-expose_spec.lua b/spec/insulate-expose_spec.lua
index 4c78e576..af372160 100644
--- a/spec/insulate-expose_spec.lua
+++ b/spec/insulate-expose_spec.lua
@@ -1,6 +1,20 @@
 assert.is_nil(package.loaded.pl)
 assert.is_nil(package.loaded['pl.file'])
 
+describe('Isolation from Busted', function()
+  it('in normal blocks', function()
+    assert.is_nil(package.loaded['pl.path'])
+  end)
+
+  insulate('in insulated blocks', function()
+    assert.is_nil(package.loaded['pl.path'])
+  end)
+
+  expose('in exposed blocks', function()
+    assert.is_nil(package.loaded['pl.path'])
+  end)
+end)
+
 describe('Tests insulation', function()
   insulate('environment inside insulate', function()
     pl = require 'pl'