diff --git a/src/lambda-handler.ts b/src/lambda-handler.ts
index 4325c41..71fa18d 100644
--- a/src/lambda-handler.ts
+++ b/src/lambda-handler.ts
@@ -40,10 +40,31 @@ const streamify_handler: StreamifyHandler = async ( event, response ) => {
 		delete args.presign;
 	}
 
-	let s3_response = await getS3File( config, key, args );
+	let s3_response;
+
+	try {
+		s3_response = await getS3File( config, key, args );
+	} catch ( e: any ) {
+		// An AccessDenied error means the file is either protected, or doesn't exist.
+		if ( e.Code === 'AccessDenied' ) {
+			const metadata = {
+				statusCode: 404,
+				headers: {
+					'Content-Type': 'text/html',
+				},
+			};
+			response = awslambda.HttpResponseStream.from( response, metadata );
+			response.write( 'File not found.' );
+			response.end();
+			return;
+		}
+		throw e;
+	}
+
 	if ( ! s3_response.Body ) {
 		throw new Error( 'No body in file.' );
 	}
+
 	let buffer = Buffer.from( await s3_response.Body.transformToByteArray() );
 
 	let { info, data } = await resizeBuffer( buffer, args );
diff --git a/tests/test-lambda.ts b/tests/test-lambda.ts
index 73fa969..e5fd4d8 100644
--- a/tests/test-lambda.ts
+++ b/tests/test-lambda.ts
@@ -14,15 +14,14 @@ test( 'Test content type headers', async () => {
 	expect( testResponseStream.contentType ).toBe( 'image/gif' );
 } );
 
-// Currently the handler will throw an error if the file is not found, rather than correctly
-// return a status code and message.
-test.failing( 'Test image not found', async () => {
+test( 'Test image not found', async () => {
 	const testResponseStream = new TestResponseStream();
 	animatedGifLambdaEvent.rawPath = '/tachyon/does-not-exist.gif';
 
 	await handler( animatedGifLambdaEvent, testResponseStream );
 
-	expect( testResponseStream.contentType ).toBe( 'image/gif' );
+	expect( testResponseStream.metadata.statusCode ).toBe( 404 );
+	expect( testResponseStream.contentType ).toBe( 'text/html' );
 } );
 
 /**