diff --git a/app/assets/javascripts/blacklists.js b/app/assets/javascripts/blacklists.js
index 66e6b09c0..506b55fd6 100644
--- a/app/assets/javascripts/blacklists.js
+++ b/app/assets/javascripts/blacklists.js
@@ -1,14 +1,14 @@
 (function() {
   Danbooru.Blacklist = {};
-  
+
   Danbooru.Blacklist.blacklists = [];
-  
+
   Danbooru.Blacklist.parse_entry = function(string) {
     var blacklist = {
-      "tags": string, 
-      "require": [], 
-      "exclude": [], 
-      "disabled": false, 
+      "tags": string,
+      "require": [],
+      "exclude": [],
+      "disabled": false,
       "hits": 0
     };
     var matches = string.match(/\S+/g) || [];
@@ -21,23 +21,23 @@
     });
     return blacklist;
   }
-  
+
   Danbooru.Blacklist.parse_entries = function() {
     var entries = (Danbooru.meta("blacklisted-tags") || "[]").replace(/(rating:[qes])\w+/, "$1").split(/,/);
-    
+
     $.each(entries, function(i, tags) {
       var blacklist = Danbooru.Blacklist.parse_entry(tags);
       Danbooru.Blacklist.blacklists.push(blacklist);
     });
   }
-  
+
   Danbooru.Blacklist.toggle = function(e) {
     $(".blacklisted").each(function(i, element) {
       var $element = $(element);
       if ($element.hasClass("blacklisted-active")) {
         var tag = $(e.target).html();
         var blacklist = Danbooru.Blacklist.parse_entry(tag);
-        
+
         if (Danbooru.Blacklist.post_match($element, blacklist)) {
           $element.removeClass("blacklisted-active");
         }
@@ -46,13 +46,13 @@
       }
     });
   }
-  
+
   Danbooru.Blacklist.update_sidebar = function() {
     $.each(this.blacklists, function(i, blacklist) {
       if (blacklist.hits === 0) {
         return;
       }
-      
+
       var item = $("<li/>");
       var link = $("<a/>");
       var count = $("<span/>");
@@ -64,17 +64,17 @@
       item.append(count);
       $("#blacklist-list").append(item);
     });
-    
+
     $("#blacklist-box").show();
   }
-  
+
   Danbooru.Blacklist.apply = function() {
     $.each(this.blacklists, function(i, blacklist) {
       blacklist.hits = 0;
     });
 
     var count = 0
-    
+
     $.each(this.posts(), function(i, post) {
       $.each(Danbooru.Blacklist.blacklists, function(i, blacklist) {
         if (Danbooru.Blacklist.post_match(post, blacklist)) {
@@ -84,39 +84,31 @@
         }
       });
     });
-    
+
     return count;
   }
-  
+
   Danbooru.Blacklist.posts = function() {
     return $(".post-preview");
   }
-  
+
   Danbooru.Blacklist.post_match = function(post, blacklist) {
     var $post = $(post);
     var tags = String($post.data("tags")).match(/\S+/g) || [];
     tags.push("rating:" + $post.data("rating"));
     tags.push("user:" + $post.data("user"));
-    
-    if (blacklist.require.length > 0 || blacklist.exclude.length > 0) {
-      if (blacklist.require.length === 0 || Danbooru.is_subset(tags, blacklist.require)) {
-        if (blacklist.exclude.length === 0 || (!Danbooru.is_subset(tags, blacklist.exclude))) {
-          return true;
-        }
-      }
-    }
-    
-    return false;
+
+    return Danbooru.is_subset(tags, blacklist.require) && !Danbooru.intersect(tags, blacklist.exclude).length;
   }
-  
+
   Danbooru.Blacklist.post_hide = function(post) {
     var $post = $(post);
     $post.addClass("blacklisted").addClass("blacklisted-active");
   }
-  
+
   Danbooru.Blacklist.initialize_all = function() {
     Danbooru.Blacklist.parse_entries();
-    
+
     if (Danbooru.Blacklist.apply() > 0) {
       Danbooru.Blacklist.update_sidebar();
     } else {
diff --git a/app/assets/javascripts/utility.js b/app/assets/javascripts/utility.js
index 3bc64f84f..c34c2ba64 100644
--- a/app/assets/javascripts/utility.js
+++ b/app/assets/javascripts/utility.js
@@ -2,27 +2,45 @@
   Danbooru.meta = function(key) {
     return $("meta[name=" + key + "]").attr("content");
   }
-  
+
   Danbooru.notice = function(msg) {
     $('#notice').html(msg).addClass("ui-state-highlight").removeClass("ui-state-error").fadeIn("fast");
   }
-  
+
   Danbooru.error = function(msg) {
     $('#notice').html(msg).removeClass("ui-state-highlight").addClass("ui-state-error").fadeIn("fast");
   }
-  
+
   Danbooru.is_subset = function(array, subarray) {
     var all = true;
-    
+
     $.each(subarray, function(i, val) {
       if ($.inArray(val, array) === -1) {
         all = false;
       }
     });
-    
+
     return all;
   }
-  
+
+  Danbooru.intersect = function(a, b) {
+    a = a.slice(0).sort();
+    b = b.slice(0).sort();
+    var result = [];
+    while (a.length > 0 && b.length > 0)
+    {
+      if (a[0] < b[0]) {
+        a.shift();
+      } else if (a[0] > b[0]) {
+        b.shift();
+      } else {
+        result.push(a.shift());
+        b.shift();
+      }
+    }
+    return result;
+  }
+
   Danbooru.without = function(array, element) {
     var temp = [];
     $.each(array, function(i, v) {
@@ -32,7 +50,7 @@
     });
     return temp;
   }
-  
+
   Danbooru.reject = function(array, f) {
     var filtered = [];
     $.each(array, function(i, x) {