diff --git a/app/models/post.rb b/app/models/post.rb
index 512e2d1dc..61031bd2f 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -1218,14 +1218,14 @@ class Post < ApplicationRecord
     end
 
     def get_count_from_cache(tags)
-      count = Cache.get(count_cache_key(tags)) # this will only have a value for multi-tag searches
-
-      if count.nil? && !tags.include?(" ")
+      if Tag.is_simple_tag?(tags)
         count = select_value_sql("SELECT post_count FROM tags WHERE name = ?", tags.to_s)
-        # set_count_in_cache(tags, count.to_i) if count
+      else
+        # this will only have a value for multi-tag searches or single metatag searches
+        count = Cache.get(count_cache_key(tags))
       end
 
-      count ? count.to_i : nil
+      count.try(:to_i)
     end
 
     def set_count_in_cache(tags, count, expiry = nil)
diff --git a/app/models/tag.rb b/app/models/tag.rb
index e4baa1896..94fcbb2f1 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -415,6 +415,12 @@ class Tag < ApplicationRecord
       end
     end
 
+    # true if query is a single "simple" tag (not a metatag, negated tag, or wildcard tag).
+    def is_simple_tag?(query)
+      q = parse_query(query)
+      (scan_query(query).size == 1) && (q[:tags][:related].size == 1)
+    end
+
     def parse_query(query, options = {})
       q = {}
 
@@ -783,6 +789,10 @@ class Tag < ApplicationRecord
   end
 
   module SearchMethods
+    def empty
+      where("tags.post_count <= 0")
+    end
+
     def nonempty
       where("tags.post_count > 0")
     end
diff --git a/script/fixes/051_purge_invalid_tags.rb b/script/fixes/051_purge_invalid_tags.rb
new file mode 100755
index 000000000..1c168ab7f
--- /dev/null
+++ b/script/fixes/051_purge_invalid_tags.rb
@@ -0,0 +1,20 @@
+#!/usr/bin/env ruby
+
+require File.expand_path(File.join(File.dirname(__FILE__), '..', '..', 'config', 'environment'))
+
+CurrentUser.user = User.system
+CurrentUser.ip_addr = "127.0.0.1"
+
+Tag.transaction do
+  empty_gentags = Tag.empty.where(category: Tag.categories.general)
+  total = empty_gentags.count
+
+  empty_gentags.find_each.with_index do |tag, i|
+    STDERR.puts %{validating "#{tag.name}" (#{i}/#{total})} if i % 1000 == 0
+
+    if tag.invalid?(:create)
+      # puts ({ name: tag.name, id: tag.id }).to_json
+      tag.delete
+    end
+  end
+end
diff --git a/test/unit/post_test.rb b/test/unit/post_test.rb
index f53d2f8b0..1092403e6 100644
--- a/test/unit/post_test.rb
+++ b/test/unit/post_test.rb
@@ -2388,13 +2388,39 @@ class PostTest < ActiveSupport::TestCase
         Danbooru.config.stubs(:blank_tag_search_fast_count).returns(nil)
         Danbooru.config.stubs(:estimate_post_counts).returns(false)
         FactoryGirl.create(:tag_alias, :antecedent_name => "alias", :consequent_name => "aaa")
-        FactoryGirl.create(:post, :tag_string => "aaa")
+        FactoryGirl.create(:post, :tag_string => "aaa", "score" => 42)
+      end
+
+      context "a single basic tag" do
+        should "return the cached count" do
+          Tag.find_or_create_by_name("aaa").update_columns(post_count: 100)
+          assert_equal(100, Post.fast_count("aaa"))
+        end
+      end
+
+      context "a single metatag" do
+        should "return the correct cached count" do
+          FactoryGirl.build(:tag, name: "score:42", post_count: -100).save(validate: false)
+          Post.set_count_in_cache("score:42", 100)
+
+          assert_equal(100, Post.fast_count("score:42"))
+        end
+      end
+
+      context "a multi-tag search" do
+        should "return the cached count, if it exists" do
+          Post.set_count_in_cache("aaa score:42", 100)
+          assert_equal(100, Post.fast_count("aaa score:42"))
+        end
+
+        should "return the true count, if not cached" do
+          assert_equal(1, Post.fast_count("aaa score:42"))
+        end
       end
 
       context "a blank search" do
         should "should execute a search" do
           Cache.delete(Post.count_cache_key(''))
-          Post.expects(:select_value_sql).with(kind_of(String), "").once.returns(nil)
           Post.expects(:fast_count_search).with("", kind_of(Hash)).once.returns(1)
           assert_equal(1, Post.fast_count(""))
         end
@@ -2428,7 +2454,6 @@ class PostTest < ActiveSupport::TestCase
           end
 
           should "execute a search" do
-            Post.expects(:select_value_sql).once.with(kind_of(String), "rating:s").returns(nil)
             Post.expects(:fast_count_search).once.with("rating:s", kind_of(Hash)).returns(1)
             assert_equal(1, Post.fast_count(""))
           end