diff --git a/jquery.tagsinput.css b/jquery.tagsinput.css
index f458143..c595e24 100644
--- a/jquery.tagsinput.css
+++ b/jquery.tagsinput.css
@@ -4,3 +4,4 @@ div.tagsinput span.tag a { font-weight: bold; color: #82ad2b; text-decoration:no
 div.tagsinput input { width:80px; margin:0px; font-family: helvetica; font-size: 13px; border:1px solid transparent; padding:5px; background: transparent; color: #000; outline:0px;  margin-right:5px; margin-bottom:5px; }
 div.tagsinput div { display:block; float: left; } 
 .tags_clear { clear: both; width: 100%; height: 0px; }
+.not_valid {background: #FBD8DB !important; color: #90111A !important;}
diff --git a/jquery.tagsinput.js b/jquery.tagsinput.js
index f1dcd12..af1fe2b 100644
--- a/jquery.tagsinput.js
+++ b/jquery.tagsinput.js
@@ -33,6 +33,10 @@
 		
 				if (options.unique) {
 					var skipTag = $(tagslist).tagExist(value);
+					if(skipTag == true) {
+					    //Marks fake input as not_valid to let styling it
+    				    $('#'+id+'_tag').addClass('not_valid');
+    				}
 				} else {
 					var skipTag = false; 
 				}
@@ -245,6 +249,14 @@
 				});
 				$(data.fake_input).blur();
 				
+				//Removes the not_valid class when user changes the value of the fake input
+				if(data.unique) {
+				    $(data.fake_input).keydown(function(event){
+				        if(event.keyCode == 8 || String.fromCharCode(event.which).match(/\w+|[áéíóúÁÉÍÓÚñÑ,/]+/)) {
+				            $(this).removeClass('not_valid');
+				        }
+				    });
+				}
 			} // if settings.interactive
 			return false;
 		});