diff --git a/packages/rollup/rollup.js b/packages/rollup/rollup.js
index fe5cd72d0..1e63394eb 100644
--- a/packages/rollup/rollup.js
+++ b/packages/rollup/rollup.js
@@ -91,15 +91,17 @@ module.exports = function(opts) {
             const usage = new Map();
             const common = new Map();
             const files = [];
+
+            const { assetFileNames = "" } = outputOptions;
             
             let to;
 
             if(!outputOptions.file && !outputOptions.dir) {
-                to = path.join(process.cwd(), outputOptions.assetFileNames || "");
+                to = path.join(process.cwd(), assetFileNames);
             } else {
                 to = path.join(
                     outputOptions.dir ? outputOptions.dir : path.dirname(outputOptions.file),
-                    outputOptions.assetFileNames
+                    assetFileNames
                 );
             }
 
diff --git a/packages/rollup/test/__snapshots__/rollup.test.js.snap b/packages/rollup/test/__snapshots__/rollup.test.js.snap
index a65d9416e..6a74ba137 100644
--- a/packages/rollup/test/__snapshots__/rollup.test.js.snap
+++ b/packages/rollup/test/__snapshots__/rollup.test.js.snap
@@ -167,6 +167,14 @@ Object {
 }
 `;
 
+exports[`/rollup.js should handle assetFileNames being undefined 1`] = `
+"/* packages/rollup/test/specimens/simple.css */
+.fooga {
+    color: red;
+}
+"
+`;
+
 exports[`/rollup.js should not output sourcemaps when they are disabled 1`] = `
 "/* packages/rollup/test/specimens/simple.css */
 .fooga {
diff --git a/packages/rollup/test/rollup.test.js b/packages/rollup/test/rollup.test.js
index 89dd0ee07..b45bf8fa7 100644
--- a/packages/rollup/test/rollup.test.js
+++ b/packages/rollup/test/rollup.test.js
@@ -87,6 +87,27 @@ describe("/rollup.js", () => {
 
         expect(read("css/assets/simple.css")).toMatchSnapshot();
     });
+
+    it("should handle assetFileNames being undefined", async () => {
+        const bundle = await rollup({
+            input   : require.resolve("./specimens/simple.js"),
+            plugins : [
+                plugin({
+                    namer,
+                    map,
+                }),
+            ],
+        });
+
+        await bundle.write({
+            format,
+            file : `${output}/assetFileNames/simple.js`,
+        });
+
+        const [ css ] = shell.ls(`${output}/assetFileNames/assets`);
+
+        expect(read(`assetFileNames/assets/${css}`)).toMatchSnapshot();
+    });
     
     it("should correctly pass to/from params for relative paths", async () => {
         const bundle = await rollup({