diff --git a/src/Bundle.js b/src/Bundle.js
index 1241678..5b05cf6 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -34,9 +34,9 @@ export default class Bundle {
 				.concat( load )
 		);
 
-		this.transformers = ensureArray( options.transform ).concat(
-			this.plugins.map( plugin => plugin.transform ).filter( Boolean )
-		);
+		this.transformers = this.plugins
+			.map( plugin => plugin.transform )
+			.filter( Boolean );
 
 		this.pending = blank();
 		this.moduleById = blank();
diff --git a/src/rollup.js b/src/rollup.js
index d31fbbe..9049174 100644
--- a/src/rollup.js
+++ b/src/rollup.js
@@ -11,6 +11,10 @@ export function rollup ( options ) {
 		throw new Error( 'You must supply options.entry to rollup' );
 	}
 
+	if ( options.transform || options.load || options.resolveId || options.resolveExternal ) {
+		throw new Error( 'The `transform`, `load`, `resolveId` and `resolveExternal` options are deprecated in favour of a unified plugin API. See https://github.com/rollup/rollup/wiki/Plugins for details' );
+	}
+
 	const bundle = new Bundle( options );
 
 	return bundle.build().then( () => {