diff --git a/lib/webpack.js b/lib/webpack.js
index 2362951c4d9..3e121f41fa9 100644
--- a/lib/webpack.js
+++ b/lib/webpack.js
@@ -32,7 +32,9 @@ const webpack = (options, callback) => {
 	}
 	let compiler;
 	if (Array.isArray(options)) {
-		compiler = new MultiCompiler(options.map(options => webpack(options)));
+		compiler = new MultiCompiler(
+			Array.from(options).map(options => webpack(options))
+		);
 	} else if (typeof options === "object") {
 		options = new WebpackOptionsDefaulter().process(options);
 
diff --git a/test/Validation.test.js b/test/Validation.test.js
index e82f8de54fa..694dcd39b33 100644
--- a/test/Validation.test.js
+++ b/test/Validation.test.js
@@ -404,6 +404,25 @@ describe("Validation", () => {
  - configuration.mode should be one of these:
    \\"development\\" | \\"production\\" | \\"none\\"
    -> Enable production optimizations or development hints."
+`)
+	);
+
+	createTestCase(
+		"holey array",
+		// eslint-disable-next-line no-sparse-arrays
+		[
+			{
+				mode: "production"
+			},
+			,
+			{
+				mode: "development"
+			}
+		],
+		msg =>
+			expect(msg).toMatchInlineSnapshot(`
+"Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
+ - configuration should be an object."
 `)
 	);
 });