diff --git a/src/posts/delete.js b/src/posts/delete.js
index a77c153cb2..40b6554b6f 100644
--- a/src/posts/delete.js
+++ b/src/posts/delete.js
@@ -181,6 +181,9 @@ module.exports = function(Posts) {
 						function(next) {
 							db.sortedSetIncrBy('cid:' + topicData.cid + ':tids:posts', -1, postData.tid, next);
 						},
+						function(next) {
+							db.sortedSetIncrBy('tid:' + postData.tid + ':posters', -1, postData.uid, next);
+						},
 						function(next) {
 							user.incrementUserPostCountBy(postData.uid, -1, next);
 						}
diff --git a/src/topics/delete.js b/src/topics/delete.js
index 97d617d878..f979d3083a 100644
--- a/src/topics/delete.js
+++ b/src/topics/delete.js
@@ -1,12 +1,12 @@
 'use strict';
 
-var async = require('async'),
-	db = require('../database'),
+var async = require('async');
+var db = require('../database');
 
-	user = require('../user'),
-	posts = require('../posts'),
-	plugins = require('../plugins'),
-	batch = require('../batch');
+var user = require('../user');
+var posts = require('../posts');
+var plugins = require('../plugins');
+var batch = require('../batch');
 
 
 module.exports = function(Topics) {
@@ -115,7 +115,8 @@ module.exports = function(Topics) {
 					'tid:' + tid + ':followers',
 					'tid:' + tid + ':posts',
 					'tid:' + tid + ':posts:votes',
-					'tid:' + tid + ':bookmarks'
+					'tid:' + tid + ':bookmarks',
+					'tid:' + tid + ':posters'
 				], next);
 			},
 			function(next) {
diff --git a/src/topics/fork.js b/src/topics/fork.js
index 948cb3207e..80143e4d46 100644
--- a/src/topics/fork.js
+++ b/src/topics/fork.js
@@ -87,7 +87,7 @@ module.exports = function(Topics) {
 				if (!exists) {
 					return next(new Error('[[error:no-topic]]'));
 				}
-				posts.getPostFields(pid, ['tid', 'timestamp', 'votes'], next);
+				posts.getPostFields(pid, ['tid', 'uid', 'timestamp', 'votes'], next);
 			},
 			function(post, next) {
 				if (!post || !post.tid) {
@@ -101,7 +101,7 @@ module.exports = function(Topics) {
 				postData = post;
 				postData.pid = pid;
 
-				Topics.removePostFromTopic(postData.tid, pid, next);
+				Topics.removePostFromTopic(postData.tid, postData, next);
 			},
 			function(next) {
 				async.parallel([
@@ -118,7 +118,7 @@ module.exports = function(Topics) {
 						posts.setPostField(pid, 'tid', tid, next);
 					},
 					function(next) {
-						Topics.addPostToTopic(tid, pid, postData.timestamp, postData.votes, next);
+						Topics.addPostToTopic(tid, postData, next);
 					}
 				], next);
 			},
diff --git a/src/topics/posts.js b/src/topics/posts.js
index 445eab4637..671c65b4c5 100644
--- a/src/topics/posts.js
+++ b/src/topics/posts.js
@@ -22,7 +22,7 @@ module.exports = function(Topics) {
 				Topics.updateTimestamp(postData.tid, postData.timestamp, next);
 			},
 			function(next) {
-				Topics.addPostToTopic(postData.tid, postData.pid, postData.timestamp, 0, next);
+				Topics.addPostToTopic(postData.tid, postData, next);
 			}
 		], callback);
 	};
@@ -264,38 +264,51 @@ module.exports = function(Topics) {
 		);
 	};
 
-	Topics.addPostToTopic = function(tid, pid, timestamp, votes, callback) {
-		Topics.getTopicField(tid, 'mainPid', function(err, mainPid) {
-			if (err) {
-				return callback(err);
-			}
-			if (!parseInt(mainPid, 10)) {
-				Topics.setTopicField(tid, 'mainPid', pid, callback);
-			} else {
-				async.parallel([
-					function(next) {
-						db.sortedSetAdd('tid:' + tid + ':posts', timestamp, pid, next);
-					},
-					function(next) {
-						db.sortedSetAdd('tid:' + tid + ':posts:votes', votes, pid, next);
-					}
-				], function(err) {
-					if (err) {
-						return callback(err);
-					}
-					Topics.updateTeaser(tid, callback);
-				});
+	Topics.addPostToTopic = function(tid, postData, callback) {
+		async.waterfall([
+			function (next) {
+				Topics.getTopicField(tid, 'mainPid', next);
+			},
+			function (mainPid, next) {
+				if (!parseInt(mainPid, 10)) {
+					Topics.setTopicField(tid, 'mainPid', postData.pid, next);
+				} else {
+					async.parallel([
+						function(next) {
+							db.sortedSetAdd('tid:' + tid + ':posts', postData.timestamp, postData.pid, next);
+						},
+						function(next) {
+							db.sortedSetAdd('tid:' + tid + ':posts:votes', postData.votes, postData.pid, next);
+						}
+					], function(err) {
+						next(err);
+					});
+				}
+			},
+			function (next) {
+				db.sortedSetIncrBy('tid:' + tid + ':posters', 1, postData.uid, next);
+			},
+			function (count, next) {
+				Topics.updateTeaser(tid, next);
 			}
-		});
+		], callback);
 	};
 
-	Topics.removePostFromTopic = function(tid, pid, callback) {
-		db.sortedSetsRemove(['tid:' + tid + ':posts', 'tid:' + tid + ':posts:votes'], pid, function(err) {
-			if (err) {
-				return callback(err);
+	Topics.removePostFromTopic = function(tid, postData, callback) {
+		async.waterfall([
+			function (next) {
+				db.sortedSetsRemove([
+					'tid:' + tid + ':posts',
+					'tid:' + tid + ':posts:votes'
+				], postData.pid, next);
+			},
+			function (next) {
+				db.sortedSetIncrBy('tid:' + tid + ':posters', -1, postData.uid, next);
+			},
+			function (count, next) {
+				Topics.updateTeaser(tid, next);
 			}
-			Topics.updateTeaser(tid, callback);
-		});
+		], callback);
 	};
 
 	Topics.getPids = function(tid, callback) {
diff --git a/src/topics/user.js b/src/topics/user.js
index 4db380efdf..09cb4a7e87 100644
--- a/src/topics/user.js
+++ b/src/topics/user.js
@@ -2,10 +2,9 @@
 
 'use strict';
 
-var async = require('async'),
-	db = require('../database'),
-	posts = require('../posts');
-
+var async = require('async');
+var db = require('../database');
+var posts = require('../posts');
 
 module.exports = function(Topics) {
 
@@ -20,22 +19,6 @@ module.exports = function(Topics) {
 	};
 
 	Topics.getUids = function(tid, callback) {
-		async.waterfall([
-			function(next) {
-				Topics.getPids(tid, next);
-			},
-			function(pids, next) {
-				posts.getPostsFields(pids, ['uid'], next);
-			},
-			function(postData, next) {
-				var uids = postData.map(function(post) {
-					return post && post.uid;
-				}).filter(function(uid, index, array) {
-					return uid && array.indexOf(uid) === index;
-				});
-
-				next(null, uids);
-			}
-		], callback);
+		db.getSortedSetRevRangeByScore('tid:' + tid + ':posters', 0, -1, '+inf', 1, callback);
 	};
 };
\ No newline at end of file
diff --git a/src/upgrade.js b/src/upgrade.js
index 68f830ef3c..77974839e6 100644
--- a/src/upgrade.js
+++ b/src/upgrade.js
@@ -10,7 +10,7 @@ var db = require('./database'),
 	schemaDate, thisSchemaDate,
 
 	// IMPORTANT: REMEMBER TO UPDATE VALUE OF latestSchema
-	latestSchema = Date.UTC(2016, 3, 14);
+	latestSchema = Date.UTC(2016, 3, 18);
 
 Upgrade.check = function(callback) {
 	db.get('schemaDate', function(err, value) {
@@ -476,6 +476,60 @@ Upgrade.upgrade = function(callback) {
 				winston.info('[2016/04/14] Group title from settings to user profile skipped!');
 				next();
 			}
+		},
+		function(next) {
+			thisSchemaDate = Date.UTC(2016, 3, 18);
+
+			if (schemaDate < thisSchemaDate) {
+				updatesMade = true;
+				winston.info('[2016/04/19] Users post count per tid');
+
+				var batch = require('./batch');
+				var topics = require('./topics');
+				var count = 0;
+				batch.processSortedSet('topics:tid', function(tids, next) {
+					winston.info('upgraded ' + count + ' topics');
+
+					async.each(tids, function(tid, next) {
+						db.delete('tid:' + tid + ':posters', function(err) {
+							if (err) {
+								return next(err);
+							}
+							topics.getPids(tid, function(err, pids) {
+								if (err) {
+									return next(err);
+								}
+
+								if (!pids.length) {
+									return next();
+								}
+
+								async.eachSeries(pids, function(pid, next) {
+									db.getObjectField('post:' + pid, 'uid', function(err, uid) {
+										if (err) {
+											return next(err);
+										}
+										if (!parseInt(uid, 10)) {
+											return next();
+										}
+										db.sortedSetIncrBy('tid:' + tid + ':posters', 1, uid, next);
+									});
+								}, next);
+							});
+						});
+					}, next);
+				}, {}, function(err) {
+					if (err) {
+						return next(err);
+					}
+
+					winston.info('[2016/04/19] Users post count per tid done');
+					Upgrade.update(thisSchemaDate, next);
+				});
+			} else {
+				winston.info('[2016/04/19] Users post count per tid skipped!');
+				next();
+			}
 		}
 		// Add new schema updates here
 		// IMPORTANT: REMEMBER TO UPDATE VALUE OF latestSchema IN LINE 24!!!