diff --git a/packages/ember-template-compiler/lib/system/compile-options.js b/packages/ember-template-compiler/lib/system/compile-options.js
index bb1deaaa862..8652309da12 100644
--- a/packages/ember-template-compiler/lib/system/compile-options.js
+++ b/packages/ember-template-compiler/lib/system/compile-options.js
@@ -16,48 +16,68 @@ export default function compileOptions(_options) {
     options.plugins = { ast: [...USER_PLUGINS, ...PLUGINS] };
   } else {
     let potententialPugins = [...USER_PLUGINS, ...PLUGINS];
+    let providedPlugins = options.plugins.ast.map(plugin => wrapLegacyPluginIfNeeded(plugin));
     let pluginsToAdd = potententialPugins.filter((plugin) => {
       return options.plugins.ast.indexOf(plugin) === -1;
     });
-    options.plugins.ast = options.plugins.ast.slice().concat(pluginsToAdd);
+    options.plugins.ast = providedPlugins.concat(pluginsToAdd);
   }
 
   return options;
 }
 
-export function registerPlugin(type, _plugin) {
-  if (type !== 'ast') {
-    throw new Error(`Attempting to register ${_plugin} as "${type}" which is not a valid Glimmer plugin type.`);
-  }
-
-  let plugin;
+function wrapLegacyPluginIfNeeded(_plugin) {
+  let plugin = _plugin;
   if (_plugin.prototype && _plugin.prototype.transform) {
     plugin = (env) => {
+      let pluginInstantiated = false;
+
       return {
         name: _plugin.constructor && _plugin.constructor.name,
 
         visitors: {
           Program(node) {
-            let plugin = new _plugin(env);
+            if (!pluginInstantiated) {
+
+              pluginInstantiated = true;
+              let plugin = new _plugin(env);
 
-            plugin.syntax = env.syntax;
+              plugin.syntax = env.syntax;
 
-            return plugin.transform(node);
+              return plugin.transform(node);
+            }
           }
         }
-        };
+      };
     };
-  } else {
-    plugin = _plugin;
+
+    plugin.__raw = _plugin;
   }
 
+  return plugin;
+}
+
+export function registerPlugin(type, _plugin) {
+  if (type !== 'ast') {
+    throw new Error(`Attempting to register ${_plugin} as "${type}" which is not a valid Glimmer plugin type.`);
+  }
+
+  for (let i = 0; i < USER_PLUGINS.length; i++) {
+    let PLUGIN = USER_PLUGINS[i];
+    if (PLUGIN === _plugin || PLUGIN.__raw === _plugin) {
+      return;
+    }
+  }
+
+  let plugin = wrapLegacyPluginIfNeeded(_plugin);
+
   USER_PLUGINS = [plugin, ...USER_PLUGINS];
 }
 
-export function removePlugin(type, PluginClass) {
+export function unregisterPlugin(type, PluginClass) {
   if (type !== 'ast') {
     throw new Error(`Attempting to unregister ${PluginClass} as "${type}" which is not a valid Glimmer plugin type.`);
   }
 
-  USER_PLUGINS = USER_PLUGINS.filter((plugin) => plugin !== PluginClass);
+  USER_PLUGINS = USER_PLUGINS.filter((plugin) => plugin !== PluginClass && plugin.__raw !== PluginClass);
 }
diff --git a/packages/ember-template-compiler/tests/system/compile_options_test.js b/packages/ember-template-compiler/tests/system/compile_options_test.js
index d678b222507..4f89be482dc 100644
--- a/packages/ember-template-compiler/tests/system/compile_options_test.js
+++ b/packages/ember-template-compiler/tests/system/compile_options_test.js
@@ -17,3 +17,4 @@ QUnit.test('has default AST plugins', function(assert) {
     assert.ok(plugins.indexOf(plugin) > -1, `includes ${plugin}`);
   }
 });
+