diff --git a/bin/lessc b/bin/lessc
index 4d3c190c..25cab56c 100755
--- a/bin/lessc
+++ b/bin/lessc
@@ -19,25 +19,9 @@ var less = require('../lib/less-node'),
     args = process.argv.slice(1),
     silent = false,
     verbose = false,
-    options = {
-        depends: false,
-        compress: false,
-        max_line_len: -1,
-        lint: false,
-        paths: [],
-        color: true,
-        strictImports: false,
-        insecure: false,
-        rootpath: '',
-        relativeUrls: false,
-        ieCompat: true,
-        strictMath: false,
-        strictUnits: false,
-        globalVars: null,
-        modifyVars: null,
-        urlArgs: '',
-        plugins: plugins
-    };
+    options = require('../lib/less/default-options')();
+
+options.plugins = plugins;
 
 if (less.options) {
     for (var i = 0, keys = Object.keys(options); i < keys.length; i++) {
@@ -431,8 +415,8 @@ function processPluginQueue() {
             case 'no-color':
                 options.color = false;
                 break;
-            case 'no-ie-compat':
-                options.ieCompat = false;
+            case 'ie-compat':
+                options.ieCompat = true;
                 break;
             case 'js':
                 options.javascriptEnabled = true;
@@ -475,10 +459,12 @@ function processPluginQueue() {
                     sourceMapOptions.sourceMapBasepath = match[2];
                 }
                 break;
+            case 'source-map-inline':
             case 'source-map-map-inline':
                 sourceMapFileInline = true;
                 options.sourceMap = true;
                 break;
+            case 'source-map-include-source':
             case 'source-map-less-inline':
                 sourceMapOptions.outputSourceFiles = true;
                 break;
diff --git a/lib/less-browser/bootstrap.js b/lib/less-browser/bootstrap.js
index 72b02c16..e1a35ba6 100644
--- a/lib/less-browser/bootstrap.js
+++ b/lib/less-browser/bootstrap.js
@@ -5,13 +5,27 @@
  */
 /*global window, document */
 
-// TODO - consider switching this out for a recommendation for this polyfill:
+// TODO - consider switching this out for a recommendation for this polyfill?
 // <script src="https://cdn.polyfill.io/v2/polyfill.min.js"></script>
 require("promise/polyfill");
 
-var options = window.less || {};
+var options = require('../less/default-options');
+
+if (window.less) {
+    for (key in window.less) {
+        if (window.less.hasOwnProperty(key)) {
+            options[key] = window.less[key];
+        }
+    }
+}
 require("./add-default-options")(window, options);
 
+options.plugins = options.plugins || [];
+
+if (window.LESS_PLUGINS) {
+    options.plugins = options.plugins.concat(window.LESS_PLUGINS);
+}
+
 var less = module.exports = require("./index")(window, options);
 
 window.less = less;
@@ -32,7 +46,7 @@ if (options.onReady) {
     if (/!watch/.test(window.location.hash)) {
         less.watch();
     }
-    // Simulate synchronous stylesheet loading by blocking page rendering
+    // Simulate synchronous stylesheet loading by hiding page rendering
     if (!options.async) {
         css = 'body { display: none !important }';
         head = document.head || document.getElementsByTagName('head')[0];
diff --git a/lib/less-node/index.js b/lib/less-node/index.js
index 4e379845..153f54b5 100644
--- a/lib/less-node/index.js
+++ b/lib/less-node/index.js
@@ -12,7 +12,7 @@ less.PluginLoader = require("./plugin-loader");
 less.fs = require("./fs");
 less.FileManager = FileManager;
 less.UrlFileManager = UrlFileManager;
-less.options = less.options || {};
+less.options = require('../less/default-options');
 
 // provide image-size functionality
 require('./image-size')(less.environment);
diff --git a/lib/less-node/lessc-helper.js b/lib/less-node/lessc-helper.js
index e9fbd843..f283421c 100644
--- a/lib/less-node/lessc-helper.js
+++ b/lib/less-node/lessc-helper.js
@@ -26,42 +26,42 @@ var lessc_helper = {
         console.log("If source is set to `-' (dash or hyphen-minus), input is read from stdin.");
         console.log("");
         console.log("options:");
-        console.log("  -h, --help               Prints help (this message) and exit.");
-        console.log("  --include-path=PATHS     Sets include paths. Separated by `:'. `;' also supported on windows.");
-        console.log("  -M, --depends            Outputs a makefile import dependency list to stdout.");
-        console.log("  --no-color               Disables colorized output.");
-        console.log("  --no-ie-compat           Disables IE compatibility checks.");
-        console.log("  --js                     Enables inline JavaScript in less files");
-        console.log("  -l, --lint               Syntax check only (lint).");
-        console.log("  -s, --silent             Suppresses output of error messages.");
-        console.log("  --strict-imports         Forces evaluation of imports.");
-        console.log("  --insecure               Allows imports from insecure https hosts.");
-        console.log("  -v, --version            Prints version number and exit.");
-        console.log("  --verbose                Be verbose.");
-        console.log("  --source-map[=FILENAME]  Outputs a v3 sourcemap to the filename (or output filename.map).");
-        console.log("  --source-map-rootpath=X  Adds this path onto the sourcemap filename and less file paths.");
-        console.log("  --source-map-basepath=X  Sets sourcemap base path, defaults to current working directory.");
-        console.log("  --source-map-less-inline Puts the less files into the map instead of referencing them.");
-        console.log("  --source-map-map-inline  Puts the map (and any less files) as a base64 data uri into the output css file.");
-        console.log("  --source-map-url=URL     Sets a custom URL to map file, for sourceMappingURL comment");
-        console.log("                           in generated CSS file.");
-        console.log("  -rp, --rootpath=URL      Sets rootpath for url rewriting in relative imports and urls");
-        console.log("                           Works with or without the relative-urls option.");
-        console.log("  -ru, --relative-urls     Re-writes relative urls to the base less file.");
-        console.log("  -sm=on|off               Turns on or off strict math, where in strict mode, math.");
-        console.log("  --strict-math=on|off     Requires brackets. This option may default to on and then");
-        console.log("                           be removed in the future.");
-        console.log("  -su=on|off               Allows mixed units, e.g. 1px+1em or 1px*1px which have units");
-        console.log("  --strict-units=on|off    that cannot be represented.");
-        console.log("  --global-var='VAR=VALUE' Defines a variable that can be referenced by the file.");
-        console.log("  --modify-var='VAR=VALUE' Modifies a variable already declared in the file.");
-        console.log("  --url-args='QUERYSTRING' Adds params into url tokens (e.g. 42, cb=42 or 'a=1&b=2')");
-        console.log("  --plugin=PLUGIN=OPTIONS  Loads a plugin. You can also omit the --plugin= if the plugin begins");
-        console.log("                           less-plugin. E.g. the clean css plugin is called less-plugin-clean-css");
-        console.log("                           once installed (npm install less-plugin-clean-css), use either with");
-        console.log("                           --plugin=less-plugin-clean-css or just --clean-css");
-        console.log("                           specify options afterwards e.g. --plugin=less-plugin-clean-css=\"advanced\"");
-        console.log("                           or --clean-css=\"advanced\"");
+        console.log("  -h, --help                   Prints help (this message) and exit.");
+        console.log("  --include-path=PATHS         Sets include paths. Separated by `:'. `;' also supported on windows.");
+        console.log("  -M, --depends                Outputs a makefile import dependency list to stdout.");
+        console.log("  --no-color                   Disables colorized output.");
+        console.log("  --ie-compat                  Enables IE8 compatibility checks.");
+        console.log("  --js                         Enables inline JavaScript in less files");
+        console.log("  -l, --lint                   Syntax check only (lint).");
+        console.log("  -s, --silent                 Suppresses output of error messages.");
+        console.log("  --strict-imports             Forces evaluation of imports.");
+        console.log("  --insecure                   Allows imports from insecure https hosts.");
+        console.log("  -v, --version                Prints version number and exit.");
+        console.log("  --verbose                    Be verbose.");
+        console.log("  --source-map[=FILENAME]      Outputs a v3 sourcemap to the filename (or output filename.map).");
+        console.log("  --source-map-rootpath=X      Adds this path onto the sourcemap filename and less file paths.");
+        console.log("  --source-map-basepath=X      Sets sourcemap base path, defaults to current working directory.");
+        console.log("  --source-map-include-source  Puts the less files into the map instead of referencing them.");
+        console.log("  --source-map-inline          Puts the map (and any less files) as a base64 data uri into the output css file.");
+        console.log("  --source-map-url=URL         Sets a custom URL to map file, for sourceMappingURL comment");
+        console.log("                               in generated CSS file.");
+        console.log("  -rp, --rootpath=URL          Sets rootpath for url rewriting in relative imports and urls");
+        console.log("                               Works with or without the relative-urls option.");
+        console.log("  -ru, --relative-urls         Re-writes relative urls to the base less file.");
+        console.log("  -sm=on|off                   Turns on or off strict math, where in strict mode, math.");
+        console.log("  --strict-math=on|off         Requires brackets. This option may default to on and then");
+        console.log("                               be removed in the future.");
+        console.log("  -su=on|off                   Allows mixed units, e.g. 1px+1em or 1px*1px which have units");
+        console.log("  --strict-units=on|off        that cannot be represented.");
+        console.log("  --global-var='VAR=VALUE'     Defines a variable that can be referenced by the file.");
+        console.log("  --modify-var='VAR=VALUE'     Modifies a variable already declared in the file.");
+        console.log("  --url-args='QUERYSTRING'     Adds params into url tokens (e.g. 42, cb=42 or 'a=1&b=2')");
+        console.log("  --plugin=PLUGIN=OPTIONS      Loads a plugin. You can also omit the --plugin= if the plugin begins");
+        console.log("                               less-plugin. E.g. the clean css plugin is called less-plugin-clean-css");
+        console.log("                               once installed (npm install less-plugin-clean-css), use either with");
+        console.log("                               --plugin=less-plugin-clean-css or just --clean-css");
+        console.log("                               specify options afterwards e.g. --plugin=less-plugin-clean-css=\"advanced\"");
+        console.log("                               or --clean-css=\"advanced\"");
         console.log("");
         console.log("-------------------------- Deprecated ----------------");
         console.log("  --line-numbers=TYPE      Outputs filename and line numbers.");
diff --git a/lib/less-rhino/index.js b/lib/less-rhino/index.js
index b59fae51..b0b745dc 100644
--- a/lib/less-rhino/index.js
+++ b/lib/less-rhino/index.js
@@ -146,23 +146,8 @@ function writeFile(filename, content) {
 // Command line integration via Rhino
 (function (args) {
 
-    var options = {
-        depends: false,
-        compress: false,
-        cleancss: false,
-        max_line_len: -1,
-        silent: false,
-        verbose: false,
-        lint: false,
-        paths: [],
-        color: true,
-        strictImports: false,
-        rootpath: '',
-        relativeUrls: false,
-        ieCompat: true,
-        strictMath: false,
-        strictUnits: false
-    };
+    var options = require('../default-options');
+
     var continueProcessing = true,
         currentErrorcode;
 
diff --git a/lib/less/default-options.js b/lib/less/default-options.js
new file mode 100644
index 00000000..09c0b3cf
--- /dev/null
+++ b/lib/less/default-options.js
@@ -0,0 +1,65 @@
+// Export a new default each time
+module.exports = function() {
+    return {
+        /* Outputs a makefile import dependency list to stdout. */
+        depends: false,
+
+        /* Compress using less built-in compression. 
+         * This does an okay job but does not utilise all the tricks of 
+         * dedicated css compression. */
+        compress: false,
+
+        /* Runs the less parser and just reports errors without any output. */
+        lint: false,
+
+        /* Sets available include paths.
+         * If the file in an @import rule does not exist at that exact location, 
+         * less will look for it at the location(s) passed to this option. 
+         * You might use this for instance to specify a path to a library which 
+         * you want to be referenced simply and relatively in the less files. */
+        paths: [],
+
+        /* color output in the terminal */
+        color: true,
+
+        /* The strictImports controls whether the compiler will allow an @import inside of either 
+         * @media blocks or (a later addition) other selector blocks.
+         * See: https://github.com/less/less.js/issues/656 */
+        strictImports: false,
+
+        /* Allow Imports from Insecure HTTPS Hosts */
+        insecure: false,
+
+        /* Allows you to add a path to every generated import and url in your css. 
+         * This does not affect less import statements that are processed, just ones 
+         * that are left in the output css. */
+        rootpath: '',
+
+        /* By default URLs are kept as-is, so if you import a file in a sub-directory 
+         * that references an image, exactly the same URL will be output in the css. 
+         * This option allows you to re-write URL's in imported files so that the 
+         * URL is always relative to the base imported file */
+        relativeUrls: false,
+
+        /* Compatibility with IE8. Used for limiting data-uri length */
+        ieCompat: false,  // true until 3.0
+
+        /* Without this option on, Less will try and process all math in your css */
+        strictMath: false,
+
+        /* Without this option, less attempts to guess at the output unit when it does maths. */
+        strictUnits: false,
+
+        /* Effectively the declaration is put at the top of your base Less file, 
+         * meaning it can be used but it also can be overridden if this variable 
+         * is defined in the file. */
+        globalVars: null,
+
+        /* As opposed to the global variable option, this puts the declaration at the
+         * end of your base file, meaning it will override anything defined in your Less file. */
+        modifyVars: null,
+
+        /* This option allows you to specify a argument to go on to every URL.  */
+        urlArgs: ''
+    }
+}
\ No newline at end of file
diff --git a/lib/less/parse.js b/lib/less/parse.js
index b83441e1..125bdff4 100644
--- a/lib/less/parse.js
+++ b/lib/less/parse.js
@@ -58,6 +58,9 @@ module.exports = function(environment, ParseTree, ImportManager) {
             var imports = new ImportManager(this, context, rootFileInfo);
             this.importManager = imports;
 
+            // TODO: allow the plugins to be just a list of paths or names
+            // Do an async plugin queue like lessc
+
             if (options.plugins) {
                 options.plugins.forEach(function(plugin) {
                     var evalResult, contents;
diff --git a/lib/less/plugin-api.js b/lib/less/plugin-api.js
index 8ef84f14..3338becf 100644
--- a/lib/less/plugin-api.js
+++ b/lib/less/plugin-api.js
@@ -1,12 +1,10 @@
-(function (root, registerPlugin) { 
+(function (root, factory) { 
     if (typeof define === 'function' && define.amd) { 
-        define([], registerPlugin);
+        define([], factory);
     } else if (typeof module === 'object' && module.exports) { 
-        module.exports = registerPlugin();
+        module.exports = factory();
     } else { 
-        if (!root.less) { root.less = {}; } 
-        if (!root.less.plugins) { root.less.plugins = []; }
-        root.less.plugins.push(registerPlugin());
+        (root.LESS_PLUGINS = root.LESS_PLUGINS || []).push(factory());
     } 
 }(this, function () {
     // Less.js Plugin object
diff --git a/lib/less/tree/dimension.js b/lib/less/tree/dimension.js
index db979a93..34b23a5b 100644
--- a/lib/less/tree/dimension.js
+++ b/lib/less/tree/dimension.js
@@ -8,6 +8,9 @@ var Node = require("./node"),
 //
 var Dimension = function (value, unit) {
     this.value = parseFloat(value);
+    if (isNaN(this.value)) {
+        throw new Error("Dimension is not a number.");
+    }
     this.unit = (unit && unit instanceof Unit) ? unit :
       new Unit(unit ? [unit] : undefined);
     this.setParent(this.unit, this);
diff --git a/test/css/plugin.css b/test/css/plugin.css
index 0c6ebe71..9dafc439 100644
--- a/test/css/plugin.css
+++ b/test/css/plugin.css
@@ -52,5 +52,18 @@
 }
 .test-simple {
   value: 3.141592653589793;
+  value: 6.28318531;
+}
+.test-conflicts {
+  value: foo;
+}
+.test-conflicts {
+  value: bar;
+}
+.test-conflicts {
+  value: foo;
+}
+.test-collection {
+  list: 32, 5, "bird";
 }
 @arbitrary value after ();
diff --git a/test/index.js b/test/index.js
index 4e13259a..09f24a14 100644
--- a/test/index.js
+++ b/test/index.js
@@ -20,7 +20,7 @@ var testMap = [
         function(name) { return name + '-all'; }],
     [{strictMath: true, relativeUrls: false, rootpath: "folder (1)/"}, "static-urls/"],
     [{strictMath: true, compress: true}, "compression/"],
-    [{strictMath: true, strictUnits: true}, "strict-units/"],
+    [{strictMath: false, strictUnits: true}, "strict-units/"],
     [{}, "legacy/"],
     [{strictMath: true, strictUnits: true, sourceMap: true, globalVars: true }, "sourcemaps/",
         lessTester.testSourcemap, null, null,
diff --git a/test/less/functions.less b/test/less/functions.less
index 4866bdca..74a2b206 100644
--- a/test/less/functions.less
+++ b/test/less/functions.less
@@ -230,3 +230,4 @@ html {
   color: mix(blue, @color1, 50%);
   color: mix(blue, @color2, 50%);
 }
+
diff --git a/test/less/plugin.less b/test/less/plugin.less
index 285c1649..1bf155d4 100644
--- a/test/less/plugin.less
+++ b/test/less/plugin.less
@@ -93,7 +93,28 @@
 }
 .test-simple {
   @plugin "./plugin/plugin-simple";
-  value: pi();
+  value: pi-anon();
+  value: (pi() * 2);
+}
+.test-conflicts {
+  @plugin "./plugin/plugin-scope1";
+  value: foo();
+}
+.test-conflicts {
+  @plugin "./plugin/plugin-scope2";
+  value: foo();
+}
+.test-conflicts {
+  @plugin "./plugin/plugin-scope1";
+  value: foo();
+}
+.test-collection {
+  @plugin "./plugin/plugin-collection";
+  @var: 32;
+  store(@var);
+  store(5);
+  store("bird");
+  list: list();
 }
 
 test-atrule("@charset"; '"utf-8"');
diff --git a/test/less/plugin/plugin-collection.js b/test/less/plugin/plugin-collection.js
new file mode 100644
index 00000000..d8deb98c
--- /dev/null
+++ b/test/less/plugin/plugin-collection.js
@@ -0,0 +1,9 @@
+var collection = [];
+
+functions.add('store', function(val) {
+    collection.push(val);  // imma store this for later
+    return false;
+});
+functions.add('list', function() {
+    return less.Value(collection);
+});
\ No newline at end of file
diff --git a/test/less/plugin/plugin-scope1.js b/test/less/plugin/plugin-scope1.js
new file mode 100644
index 00000000..b9aa5804
--- /dev/null
+++ b/test/less/plugin/plugin-scope1.js
@@ -0,0 +1,3 @@
+functions.add('foo', function() {
+    return "foo";
+});
\ No newline at end of file
diff --git a/test/less/plugin/plugin-scope2.js b/test/less/plugin/plugin-scope2.js
new file mode 100644
index 00000000..a7faa74d
--- /dev/null
+++ b/test/less/plugin/plugin-scope2.js
@@ -0,0 +1,3 @@
+functions.add('foo', function() {
+    return "bar";
+});
\ No newline at end of file
diff --git a/test/less/plugin/plugin-simple.js b/test/less/plugin/plugin-simple.js
index 340b9b3a..6c059e35 100644
--- a/test/less/plugin/plugin-simple.js
+++ b/test/less/plugin/plugin-simple.js
@@ -1,3 +1,7 @@
-functions.add('pi', function() {
+functions.add('pi-anon', function() {
     return Math.PI;
+});
+
+functions.add('pi', function() {
+    return less.Dimension(Math.PI);
 });
\ No newline at end of file