diff --git a/README.md b/README.md
index b8ad6a08a14..53183ad39b4 100644
--- a/README.md
+++ b/README.md
@@ -937,6 +937,12 @@ Reveal.configure({ slideNumber: true });
 //  "c/t": 	flattened slide number / total slides
 Reveal.configure({ slideNumber: 'c/t' });
 
+// You can provide a function to fully customize the number:
+Reveal.configure({ slideNumber: function() {
+	// Ignore numbering of vertical slides
+    return [ Reveal.getIndices().h ];
+}});
+
 // Control which views the slide number displays on using the "showSlideNumber" value:
 //     "all": show on all views (default)
 // "speaker": only show slide numbers on speaker notes view
diff --git a/js/reveal.js b/js/reveal.js
index 8feb45d83e8..237c0c435a9 100644
--- a/js/reveal.js
+++ b/js/reveal.js
@@ -67,18 +67,31 @@
 			progress: true,
 
 			// Display the page number of the current slide
+			// - true:    Show slide number
+			// - false:   Hide slide number
+			//
+			// Can optionally be set as a string that specifies the number formatting:
+			// - "h.v":	  Horizontal . vertical slide number (default)
+			// - "h/v":	  Horizontal / vertical slide number
+			// - "c":	  Flattened slide number
+			// - "c/t":	  Flattened slide number / total slides
+			//
+			// Alternatively, you can provide a function that returns the slide
+			// number for the current slide. The function needs to return an array
+			// with one string [slideNumber] or three strings [n1,delimiter,n2].
+			// See #formatSlideNumber().
 			slideNumber: false,
 
-			// Use 1 based indexing for # links to match slide number (default is zero
-			// based)
-			hashOneBasedIndex: false,
-
-			// Controls which contexts the slide number should appear in
+			// Can be used to limit the contexts in which the slide number appears
 			// - "all":      Always show the slide number
 			// - "print":    Only when printing to PDF
 			// - "speaker":  Only in the speaker view
 			showSlideNumber: 'all',
 
+			// Use 1 based indexing for # links to match slide number (default is zero
+			// based)
+			hashOneBasedIndex: false,
+
 			// Add the current slide number to the URL hash so that reloading the
 			// page/copying the URL will return you to the same slide
 			hash: false,
@@ -3262,16 +3275,7 @@
 
 
 	/**
-	 * Updates the slide number div to reflect the current slide.
-	 *
-	 * The following slide number formats are available:
-	 *  "h.v":	horizontal . vertical slide number (default)
-	 *  "h/v":	horizontal / vertical slide number
-	 *    "c":	flattened slide number
-	 *  "c/t":	flattened slide number / total slides
-	 *
-	 * Alternatively, config.slideNumber can be a function returning a
-	 * three-element array with arguments to formatSlideNumber().
+	 * Updates the slide number to match the current slide.
 	 */
 	function updateSlideNumber() {
 
@@ -3281,9 +3285,10 @@
 			var value;
 			var format = 'h.v';
 
-			if ( typeof config.slideNumber === 'function' ) {
+			if( typeof config.slideNumber === 'function' ) {
 				value = config.slideNumber();
-			} else {
+			}
+			else {
 				// Check if a custom number format is available
 				if( typeof config.slideNumber === 'string' ) {
 					format = config.slideNumber;