The default image version can be specified by dropping the width value

README.md

@@ -23,7 +23,7 @@ npm install responsively-lazy
 bower install responsively-lazy
 ```
 
-The library does not have any dependencies and it's just 1.1kb gzipped and minified.
+The library does not have any dependencies, and it's just 1.1kb gzipped and minified.
 
 ## Usage
 
@@ -51,7 +51,7 @@ You can list image versions in the [WebP format](https://en.wikipedia.org/wiki/W
 
 ## A new concept
 
-Responsively Lazy is very different from the other lazy loading libraries. They make you break your HTML by removing the `src` attribute, or make you put tiny version there or make you use `<noscript>` to make your images appear in Google Images. The following code has worked for ages. 
+Responsively Lazy is very different from the other lazy loading libraries. They make you break your HTML by removing the `src` attribute, or make you put tiny version there or make you use `<noscript>` to make your images appear in Google Images. The following code has worked for ages: 
 ```
 <img src="image.jpg" />
 ```

package.json

@@ -1,7 +1,7 @@
 {
     "name": "responsively-lazy",
     "title": "Responsively Lazy",
-    "version": "1.1.0",
+    "version": "1.2.0",
     "description": "Lazy load responsive images",
     "homepage": "http://ivopetkov.com/b/lazy-load-responsive-images/",
     "author": {

responsivelyLazy.js

@@ -39,8 +39,13 @@ if (typeof responsivelyLazy === 'undefined') {
                     for (var j = 0; j < optionsCount; j++) {
                         var option = options[j].trim();
                         var spaceIndex = option.lastIndexOf(' ');
-                        var optionImage = option.substr(0, spaceIndex);
-                        var optionWidth = parseInt(option.substr(spaceIndex + 1, option.length - spaceIndex - 2), 10);
+                        if (spaceIndex === -1) {
+                            var optionImage = option;
+                            var optionWidth = 999998;
+                        } else {
+                            var optionImage = option.substr(0, spaceIndex);
+                            var optionWidth = parseInt(option.substr(spaceIndex + 1, option.length - spaceIndex - 2), 10);
+                        }
                         var add = false;
                         if (optionImage.indexOf('.webp', optionImage.length - 5) !== -1) {
                             if (responsivelyLazy.hasWebPSupport) {