diff --git a/tools/build-plugin.js b/tools/build-plugin.js
index 37fcc5cf62..2843c88da1 100644
--- a/tools/build-plugin.js
+++ b/tools/build-plugin.js
@@ -4,7 +4,7 @@ var files = require('./files.js');
 var buildmessage = require('./buildmessage.js');
 var _ = require('underscore');
 
-exports.BuildPluginDefintion = function (options, factoryFunction) {
+exports.BuildPluginDefinition = function (options, factoryFunction) {
   var self = this;
   self.id = options.id;
   self.isopack = options.isopack;
@@ -14,7 +14,7 @@ exports.BuildPluginDefintion = function (options, factoryFunction) {
   self.buildPluginClass = options.buildPluginClass;
   self.factoryFunction = factoryFunction;
 };
-_.extend(exports.BuildPluginDefintion.prototype, {
+_.extend(exports.BuildPluginDefinition.prototype, {
   instantiatePlugin: function () {
     var self = this;
     // XXX BBP proper error handling --- this is running user-supplied plugin
diff --git a/tools/isopack.js b/tools/isopack.js
index a1d39555d8..676fd2c5fa 100644
--- a/tools/isopack.js
+++ b/tools/isopack.js
@@ -13,7 +13,7 @@ var packageMapModule = require('./package-map.js');
 var colonConverter = require('./colon-converter.js');
 var compilerPluginModule = require('./compiler-plugin.js');
 var linterPluginModule = require('./linter-plugin.js');
-var BuildPluginDefintion = require('./build-plugin.js').BuildPluginDefintion;
+var BuildPluginDefinition = require('./build-plugin.js').BuildPluginDefinition;
 var Future = require('fibers/future');
 var Console = require('./console.js').Console;
 var Profile = require('./profile.js').Profile;
@@ -661,7 +661,7 @@ _.extend(Isopack.prototype, {
         // We're finally done validating!  Save the processor plugin, and mark
         // all its extensions as used.
         self.sourceProcessors[type][processorPluginId] =
-          new BuildPluginDefintion({
+          new BuildPluginDefinition({
             id: processorPluginId,
             isopack: self,
             extensions: options.extensions,