diff --git a/lib/model.js b/lib/model.js
index a83bb1a..a2f8033 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -407,6 +407,8 @@ module.exports = function loadModel( file, callback ) {
 			case 'application/octet-stream':
 				readBinary( file );
 			break;
+			default:
+				callback("Unhandled mime type, rename file extension to either .txt or .bin");
 		}
 	}
 	init( file );