diff --git a/libraries/o-error/index.js b/libraries/o-error/index.js
index 0f00eb0600..b6cf0362b1 100644
--- a/libraries/o-error/index.js
+++ b/libraries/o-error/index.js
@@ -1,7 +1,5 @@
 'use strict'
 
-var util = require('util')
-
 /**
  * Make custom error types that pass `instanceof` checks, have stack traces,
  * support custom messages and properties, and support wrapping errors (causes).
@@ -9,10 +7,6 @@ var util = require('util')
  * @module
  */
 
-//
-// For ES6+ Classes
-//
-
 /**
  * A base class for custom errors that handles:
  *
@@ -96,45 +90,4 @@ OError.getFullInfo = getFullInfo
 OError.getFullStack = getFullStack
 OError.hasCauseInstanceOf = hasCauseInstanceOf
 
-//
-// For ES5
-//
-
-function extendErrorType (base, name, builder) {
-  var errorConstructor = function () {
-    Error.captureStackTrace && Error.captureStackTrace(this, this.constructor)
-    if (builder) builder.apply(this, arguments)
-    this.name = name
-  }
-
-  util.inherits(errorConstructor, base)
-
-  errorConstructor.prototype.withCause = function (cause) {
-    this.cause = cause
-    if (this.message && cause.message) {
-      this.message += ': ' + cause.message
-    }
-    return this
-  }
-
-  return errorConstructor
-}
-
-function defineErrorType (name, builder) {
-  return extendErrorType(Error, name, builder)
-}
-
-function extendErrorTypeIn (container, base, name, builder) {
-  container[name] = extendErrorType(base, name, builder)
-}
-
-function defineErrorTypeIn (container, name, builder) {
-  extendErrorTypeIn(container, Error, name, builder)
-}
-
-OError.extend = extendErrorType
-OError.define = defineErrorType
-OError.extendIn = extendErrorTypeIn
-OError.defineIn = defineErrorTypeIn
-
 module.exports = OError
diff --git a/libraries/o-error/test/error-type.test.js b/libraries/o-error/test/error-type.test.js
deleted file mode 100644
index 9526201639..0000000000
--- a/libraries/o-error/test/error-type.test.js
+++ /dev/null
@@ -1,115 +0,0 @@
-'use strict'
-
-var OError = require('..')
-const { expectError } = require('./support')
-
-describe('OError', function () {
-  it('defines a custom error type', function () {
-    var CustomError = OError.define('CustomError')
-
-    function doSomethingBad () {
-      throw new CustomError()
-    }
-
-    try {
-      doSomethingBad()
-      expect.fail('should have thrown')
-    } catch (e) {
-      expectError(e, {
-        name: 'CustomError',
-        klass: CustomError,
-        message: 'CustomError',
-        firstFrameRx: /doSomethingBad/
-      })
-    }
-  })
-
-  it('defines a custom error type with a message', function () {
-    var CustomError = OError.define('CustomError', function (x) {
-      this.message = 'x=' + x
-      this.x = x
-    })
-
-    function doSomethingBad () {
-      throw new CustomError('foo')
-    }
-
-    try {
-      doSomethingBad()
-      expect.fail('should have thrown')
-    } catch (e) {
-      expect(e.toString()).to.equal('CustomError: x=foo')
-      expect(e.message).to.equal('x=foo')
-      expect(e.x).to.equal('foo')
-    }
-  })
-
-  it('defines extended error type', function () {
-    var BaseError = OError.define('BaseError')
-    var DerivedError = OError.extend(BaseError, 'DerivedError')
-
-    function doSomethingBad () {
-      throw new DerivedError()
-    }
-
-    try {
-      doSomethingBad()
-      expect.fail('should have thrown')
-    } catch (e) {
-      expect(e.toString()).to.equal('DerivedError')
-    }
-  })
-
-  it('defines error types in a container object', function () {
-    var SomeClass = {}
-    OError.defineIn(SomeClass, 'CustomError')
-
-    function doSomethingBad () {
-      throw new SomeClass.CustomError()
-    }
-
-    try {
-      doSomethingBad()
-      expect.fail('should have thrown')
-    } catch (e) {
-      expect(e.toString()).to.equal('CustomError')
-    }
-  })
-
-  it('extends error types in a container object', function () {
-    var SomeClass = {}
-    OError.defineIn(SomeClass, 'CustomError', function (payload) {
-      this.message = 'custom error'
-      this.payload = payload
-    })
-    OError.extendIn(SomeClass, SomeClass.CustomError, 'DerivedCustomError',
-      function (payload) {
-        SomeClass.CustomError.call(this, payload)
-        this.message = 'derived custom error'
-      })
-
-    function doSomethingBad () {
-      throw new SomeClass.CustomError(123)
-    }
-
-    try {
-      doSomethingBad()
-      expect.fail('should have thrown')
-    } catch (e) {
-      expect(e.toString()).to.equal('CustomError: custom error')
-      expect(e.payload).to.equal(123)
-    }
-
-    function doSomethingBadWithDerived () {
-      throw new SomeClass.DerivedCustomError(456)
-    }
-
-    try {
-      doSomethingBadWithDerived()
-      expect.fail('should have thrown')
-    } catch (e) {
-      expect(e.toString()).to.equal('DerivedCustomError: derived custom error')
-      expect(e.payload).to.equal(456)
-    }
-  })
-})
diff --git a/libraries/o-error/test/error-type-util.test.js b/libraries/o-error/test/o-error-util.test.js
similarity index 100%
rename from libraries/o-error/test/error-type-util.test.js
rename to libraries/o-error/test/o-error-util.test.js
diff --git a/libraries/o-error/test/error-type-class.test.js b/libraries/o-error/test/o-error.test.js
similarity index 100%
rename from libraries/o-error/test/error-type-class.test.js
rename to libraries/o-error/test/o-error.test.js
diff --git a/libraries/o-error/test/support/index.js b/libraries/o-error/test/support/index.js
index 24cbc45270..502348acdf 100644
--- a/libraries/o-error/test/support/index.js
+++ b/libraries/o-error/test/support/index.js
@@ -4,7 +4,7 @@ var chai = require('chai')
 
 global.expect = chai.expect
 
-exports.expectError = function errorTypeExpectError (e, expected) {
+exports.expectError = function OErrorExpectError (e, expected) {
   // should set the name to the error's name
   expect(e.name).to.equal(expected.name)