diff --git a/packages/babel-helpers/src/helpers.js b/packages/babel-helpers/src/helpers.js
index 2ac4251c02..566aa199b0 100644
--- a/packages/babel-helpers/src/helpers.js
+++ b/packages/babel-helpers/src/helpers.js
@@ -700,3 +700,70 @@ helpers.toPropertyKey = defineHelper(`
     }
   }
 `);
+
+/**
+ * Add a helper that will throw a useful error if the transform fails to detect the class
+ * property assignment, so users know something failed.
+ */
+helpers.initializerWarningHelper = defineHelper(`
+    export default function _initializerWarningHelper(descriptor, context){
+        throw new Error(
+          'Decorating class property failed. Please ensure that ' +
+          'proposal-class-properties is enabled and set to use loose mode. ' +
+          'To use proposal-class-properties in spec mode with decorators, wait for ' +
+          'the next major version of decorators in stage 2.'
+        );
+    }
+`);
+
+/**
+ * Add a helper to call as a replacement for class property definition.
+ */
+helpers.initializerDefineProperty = defineHelper(`
+    export default function _initializerDefineProperty(target, property, descriptor, context){
+        if (!descriptor) return;
+
+        Object.defineProperty(target, property, {
+            enumerable: descriptor.enumerable,
+            configurable: descriptor.configurable,
+            writable: descriptor.writable,
+            value: descriptor.initializer ? descriptor.initializer.call(context) : void 0,
+        });
+    }
+`);
+
+/**
+ * Add a helper to take an initial descriptor, apply some decorators to it, and optionally
+ * define the property.
+ */
+helpers.applyDecoratedDescriptor = defineHelper(`
+    export default function _applyDecoratedDescriptor(target, property, decorators, descriptor, context){
+        var desc = {};
+        Object['ke' + 'ys'](descriptor).forEach(function(key){
+            desc[key] = descriptor[key];
+        });
+        desc.enumerable = !!desc.enumerable;
+        desc.configurable = !!desc.configurable;
+        if ('value' in desc || desc.initializer){
+            desc.writable = true;
+        }
+
+        desc = decorators.slice().reverse().reduce(function(desc, decorator){
+            return decorator(target, property, desc) || desc;
+        }, desc);
+
+        if (context && desc.initializer !== void 0){
+            desc.value = desc.initializer ? desc.initializer.call(context) : void 0;
+            desc.initializer = undefined;
+        }
+
+        if (desc.initializer === void 0){
+            // This is a hack to avoid this being processed by 'transform-runtime'.
+            // See issue #9.
+            Object['define' + 'Property'](target, property, desc);
+            desc = null;
+        }
+
+        return desc;
+    }
+`);
diff --git a/packages/babel-plugin-proposal-decorators/src/index.js b/packages/babel-plugin-proposal-decorators/src/index.js
index 127e358863..0a6d1f6c60 100644
--- a/packages/babel-plugin-proposal-decorators/src/index.js
+++ b/packages/babel-plugin-proposal-decorators/src/index.js
@@ -26,116 +26,7 @@ const buildGetObjectInitializer = template(`
     })
 `);
 
-const buildInitializerWarningHelper = template(`
-    function NAME(descriptor, context){
-        throw new Error(
-          'Decorating class property failed. Please ensure that ' +
-          'proposal-class-properties is enabled and set to use loose mode. ' +
-          'To use proposal-class-properties in spec mode with decorators, wait for ' +
-          'the next major version of decorators in stage 2.'
-        );
-    }
-`);
-
-const buildInitializerDefineProperty = template(`
-    function NAME(target, property, descriptor, context){
-        if (!descriptor) return;
-
-        Object.defineProperty(target, property, {
-            enumerable: descriptor.enumerable,
-            configurable: descriptor.configurable,
-            writable: descriptor.writable,
-            value: descriptor.initializer ? descriptor.initializer.call(context) : void 0,
-        });
-    }
-`);
-
-const buildApplyDecoratedDescriptor = template(`
-    function NAME(target, property, decorators, descriptor, context){
-        var desc = {};
-        Object['ke' + 'ys'](descriptor).forEach(function(key){
-            desc[key] = descriptor[key];
-        });
-        desc.enumerable = !!desc.enumerable;
-        desc.configurable = !!desc.configurable;
-        if ('value' in desc || desc.initializer){
-            desc.writable = true;
-        }
-
-        desc = decorators.slice().reverse().reduce(function(desc, decorator){
-            return decorator(target, property, desc) || desc;
-        }, desc);
-
-        if (context && desc.initializer !== void 0){
-            desc.value = desc.initializer ? desc.initializer.call(context) : void 0;
-            desc.initializer = undefined;
-        }
-
-        if (desc.initializer === void 0){
-            // This is a hack to avoid this being processed by 'transform-runtime'.
-            // See issue #9.
-            Object['define' + 'Property'](target, property, desc);
-            desc = null;
-        }
-
-        return desc;
-    }
-`);
-
 export default function() {
-  /**
-   * Add a helper to take an initial descriptor, apply some decorators to it, and optionally
-   * define the property.
-   */
-  function ensureApplyDecoratedDescriptorHelper(path, state) {
-    if (!state.applyDecoratedDescriptor) {
-      state.applyDecoratedDescriptor = path.scope.generateUidIdentifier(
-        "applyDecoratedDescriptor",
-      );
-      const helper = buildApplyDecoratedDescriptor({
-        NAME: state.applyDecoratedDescriptor,
-      });
-      path.scope.getProgramParent().path.unshiftContainer("body", helper);
-    }
-
-    return state.applyDecoratedDescriptor;
-  }
-
-  /**
-   * Add a helper to call as a replacement for class property definition.
-   */
-  function ensureInitializerDefineProp(path, state) {
-    if (!state.initializerDefineProp) {
-      state.initializerDefineProp = path.scope.generateUidIdentifier(
-        "initDefineProp",
-      );
-      const helper = buildInitializerDefineProperty({
-        NAME: state.initializerDefineProp,
-      });
-      path.scope.getProgramParent().path.unshiftContainer("body", helper);
-    }
-
-    return state.initializerDefineProp;
-  }
-
-  /**
-   * Add a helper that will throw a useful error if the transform fails to detect the class
-   * property assignment, so users know something failed.
-   */
-  function ensureInitializerWarning(path, state) {
-    if (!state.initializerWarningHelper) {
-      state.initializerWarningHelper = path.scope.generateUidIdentifier(
-        "initializerWarningHelper",
-      );
-      const helper = buildInitializerWarningHelper({
-        NAME: state.initializerWarningHelper,
-      });
-      path.scope.getProgramParent().path.unshiftContainer("body", helper);
-    }
-
-    return state.initializerWarningHelper;
-  }
-
   /**
    * If the decorator expressions are non-identifiers, hoist them to before the class so we can be sure
    * that they are evaluated in order.
@@ -260,35 +151,32 @@ export default function() {
               t.blockStatement([t.returnStatement(node.value)]),
             )
           : t.nullLiteral();
-        node.value = t.callExpression(ensureInitializerWarning(path, state), [
-          descriptor,
-          t.thisExpression(),
-        ]);
+        node.value = t.callExpression(
+          state.addHelper("initializerWarningHelper"),
+          [descriptor, t.thisExpression()],
+        );
 
         acc = acc.concat([
           t.assignmentExpression(
             "=",
             descriptor,
-            t.callExpression(
-              ensureApplyDecoratedDescriptorHelper(path, state),
-              [
-                target,
-                property,
-                t.arrayExpression(decorators.map(dec => dec.expression)),
-                t.objectExpression([
-                  t.objectProperty(
-                    t.identifier("enumerable"),
-                    t.booleanLiteral(true),
-                  ),
-                  t.objectProperty(t.identifier("initializer"), initializer),
-                ]),
-              ],
-            ),
+            t.callExpression(state.addHelper("applyDecoratedDescriptor"), [
+              target,
+              property,
+              t.arrayExpression(decorators.map(dec => dec.expression)),
+              t.objectExpression([
+                t.objectProperty(
+                  t.identifier("enumerable"),
+                  t.booleanLiteral(true),
+                ),
+                t.objectProperty(t.identifier("initializer"), initializer),
+              ]),
+            ]),
           ),
         ]);
       } else {
         acc = acc.concat(
-          t.callExpression(ensureApplyDecoratedDescriptorHelper(path, state), [
+          t.callExpression(state.addHelper("applyDecoratedDescriptor"), [
             target,
             property,
             t.arrayExpression(decorators.map(dec => dec.expression)),
@@ -367,21 +255,13 @@ export default function() {
       },
 
       AssignmentExpression(path, state) {
-        if (!state.initializerWarningHelper) return;
-
         if (!path.get("left").isMemberExpression()) return;
         if (!path.get("left.property").isIdentifier()) return;
         if (!path.get("right").isCallExpression()) return;
-        if (
-          !path
-            .get("right.callee")
-            .isIdentifier({ name: state.initializerWarningHelper.name })
-        ) {
-          return;
-        }
+        if (!path.get("right.callee").isIdentifier()) return;
 
         path.replaceWith(
-          t.callExpression(ensureInitializerDefineProp(path, state), [
+          t.callExpression(state.addHelper("initializerDefineProperty"), [
             path.get("left.object").node,
             t.stringLiteral(path.get("left.property").node.name),
             path.get("right.arguments")[0].node,