diff --git a/app/models/artist.rb b/app/models/artist.rb
index 6d5462ed6..b747eeefe 100644
--- a/app/models/artist.rb
+++ b/app/models/artist.rb
@@ -58,7 +58,7 @@ class Artist < ActiveRecord::Base
 
     module ClassMethods
       def normalize_name(name)
-        name.to_s.downcase.strip.gsub(/ /, '_')
+        name.to_s.mb_chars.downcase.strip.gsub(/ /, '_')
       end
     end
 
diff --git a/app/models/ban.rb b/app/models/ban.rb
index 98d5a5231..223705f2a 100644
--- a/app/models/ban.rb
+++ b/app/models/ban.rb
@@ -16,7 +16,7 @@ class Ban < ActiveRecord::Base
     return q if params.blank?
 
     if params[:banner_name]
-      q = q.where("banner_id = (select _.id from users _ where lower(_.name) = ?)", params[:banner_name].downcase)
+      q = q.where("banner_id = (select _.id from users _ where lower(_.name) = ?)", params[:banner_name].mb_chars.downcase)
     end
 
     if params[:banner_id]
@@ -24,7 +24,7 @@ class Ban < ActiveRecord::Base
     end
 
     if params[:user_name]
-      q = q.where("user_id = (select _.id from users _ where lower(_.name) = ?)", params[:user_name].downcase)
+      q = q.where("user_id = (select _.id from users _ where lower(_.name) = ?)", params[:user_name].mb_chars.downcase)
     end
 
     if params[:user_id]
diff --git a/app/models/dmail.rb b/app/models/dmail.rb
index 2889a45d8..e79597bf4 100644
--- a/app/models/dmail.rb
+++ b/app/models/dmail.rb
@@ -111,11 +111,11 @@ class Dmail < ActiveRecord::Base
     end
 
     def to_name_matches(name)
-      where("to_id = (select _.id from users _ where lower(_.name) = ?)", name.downcase)
+      where("to_id = (select _.id from users _ where lower(_.name) = ?)", name.mb_chars.downcase)
     end
 
     def from_name_matches(name)
-      where("from_id = (select _.id from users _ where lower(_.name) = ?)", name.downcase)
+      where("from_id = (select _.id from users _ where lower(_.name) = ?)", name.mb_chars.downcase)
     end
 
     def search(params)
diff --git a/app/models/janitor_trial.rb b/app/models/janitor_trial.rb
index cd16c8a31..1ec3ab20c 100644
--- a/app/models/janitor_trial.rb
+++ b/app/models/janitor_trial.rb
@@ -12,7 +12,7 @@ class JanitorTrial < ActiveRecord::Base
     return q if params.blank?
 
     if params[:user_name]
-      q = q.where("user_id = (select _.id from users _ where lower(_.name) = ?)", params[:user_name].downcase)
+      q = q.where("user_id = (select _.id from users _ where lower(_.name) = ?)", params[:user_name].mb_chars.downcase)
     end
 
     if params[:user_id]
diff --git a/app/models/pool.rb b/app/models/pool.rb
index a5fcd0ad8..9983a70b6 100644
--- a/app/models/pool.rb
+++ b/app/models/pool.rb
@@ -58,7 +58,7 @@ class Pool < ActiveRecord::Base
     if name =~ /^\d+$/
       name.to_i
     else
-      select_value_sql("SELECT id FROM pools WHERE lower(name) = ?", name.downcase.tr(" ", "_")).to_i
+      select_value_sql("SELECT id FROM pools WHERE lower(name) = ?", name.mb_chars.downcase.tr(" ", "_")).to_i
     end
   end
 
@@ -91,7 +91,7 @@ class Pool < ActiveRecord::Base
     if name =~ /^\d+$/
       where("id = ?", name.to_i).first
     elsif name
-      where("lower(name) = ?", normalize_name(name).downcase).first
+      where("lower(name) = ?", normalize_name(name).mb_chars.downcase).first
     else
       nil
     end
diff --git a/app/models/pool_version.rb b/app/models/pool_version.rb
index 04a419fa7..9755781e9 100644
--- a/app/models/pool_version.rb
+++ b/app/models/pool_version.rb
@@ -20,7 +20,7 @@ class PoolVersion < ActiveRecord::Base
       end
 
       if params[:updater_name].present?
-        q = q.where("updater_id = (select _.id from users _ where lower(_.name) = ?)", params[:updater_name].downcase)
+        q = q.where("updater_id = (select _.id from users _ where lower(_.name) = ?)", params[:updater_name].mb_chars.downcase)
       end
 
       if params[:pool_id].present?
diff --git a/app/models/post.rb b/app/models/post.rb
index a00338599..7ed140238 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -973,7 +973,7 @@ class Post < ActiveRecord::Base
     end
 
     def updater_name_matches(name)
-      where("updater_id = (select _.id from users _ where lower(_.name) = ?)", name.downcase)
+      where("updater_id = (select _.id from users _ where lower(_.name) = ?)", name.mb_chars.downcase)
     end
 
     def after_id(num)
diff --git a/app/models/post_appeal.rb b/app/models/post_appeal.rb
index ac9986b68..f44b3f6e5 100644
--- a/app/models/post_appeal.rb
+++ b/app/models/post_appeal.rb
@@ -27,7 +27,7 @@ class PostAppeal < ActiveRecord::Base
       end
 
       if params[:creator_name].present?
-        q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].downcase)
+        q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].mb_chars.downcase)
       end
 
       if params[:post_id].present?
diff --git a/app/models/post_flag.rb b/app/models/post_flag.rb
index 5d5aba1c2..800d8c988 100644
--- a/app/models/post_flag.rb
+++ b/app/models/post_flag.rb
@@ -36,7 +36,7 @@ class PostFlag < ActiveRecord::Base
       end
 
       if params[:creator_name].present?
-        q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].downcase)
+        q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].mb_chars.downcase)
       end
 
       if params[:post_id].present?
diff --git a/app/models/post_version.rb b/app/models/post_version.rb
index 73882d9cb..1e7dff2e8 100644
--- a/app/models/post_version.rb
+++ b/app/models/post_version.rb
@@ -9,7 +9,7 @@ class PostVersion < ActiveRecord::Base
     end
 
     def updater_name(name)
-      where("updater_id = (select _.id from users _ where lower(_.name) = ?)", name.downcase)
+      where("updater_id = (select _.id from users _ where lower(_.name) = ?)", name.mb_chars.downcase)
     end
 
     def search(params)
diff --git a/app/models/tag.rb b/app/models/tag.rb
index 442873390..eb8698e87 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -121,7 +121,7 @@ class Tag < ActiveRecord::Base
 
   module NameMethods
     def normalize_name(name)
-      name.downcase.tr(" ", "_").gsub(/\A[-~]+/, "").gsub(/\*/, "")
+      name.mb_chars.downcase.tr(" ", "_").gsub(/\A[-~]+/, "").gsub(/\*/, "").to_s
     end
 
     def find_or_create_by_name(name, options = {})
@@ -233,10 +233,10 @@ class Tag < ActiveRecord::Base
 
     def parse_tag(tag, output)
       if tag[0] == "-" && tag.size > 1
-        output[:exclude] << tag[1..-1].downcase
+        output[:exclude] << tag[1..-1].mb_chars.downcase
 
       elsif tag[0] == "~" && tag.size > 1
-        output[:include] << tag[1..-1].downcase
+        output[:include] << tag[1..-1].mb_chars.downcase
 
       elsif tag =~ /\*/
         matches = Tag.name_matches(tag.downcase).all(:select => "name", :limit => Danbooru.config.tag_query_limit, :order => "post_count DESC").map(&:name)
@@ -244,7 +244,7 @@ class Tag < ActiveRecord::Base
         output[:include] += matches
 
       else
-        output[:related] << tag.downcase
+        output[:related] << tag.mb_chars.downcase
       end
     end
 
@@ -431,7 +431,7 @@ class Tag < ActiveRecord::Base
 
   module SearchMethods
     def name_matches(name)
-      where("name LIKE ? ESCAPE E'\\\\'", name.downcase.to_escaped_for_sql_like)
+      where("name LIKE ? ESCAPE E'\\\\'", name.mb_chars.downcase.to_escaped_for_sql_like)
     end
 
     def named(name)
diff --git a/app/models/tag_alias.rb b/app/models/tag_alias.rb
index fd18a3807..344f7216b 100644
--- a/app/models/tag_alias.rb
+++ b/app/models/tag_alias.rb
@@ -12,7 +12,7 @@ class TagAlias < ActiveRecord::Base
 
   module SearchMethods
     def name_matches(name)
-      where("(antecedent_name like ? escape E'\\\\' or consequent_name like ? escape E'\\\\')", name.downcase.to_escaped_for_sql_like, name.downcase.to_escaped_for_sql_like)
+      where("(antecedent_name like ? escape E'\\\\' or consequent_name like ? escape E'\\\\')", name.mb_chars.downcase.to_escaped_for_sql_like, name.downcase.to_escaped_for_sql_like)
     end
     
     def active
diff --git a/app/models/tag_subscription.rb b/app/models/tag_subscription.rb
index bdf733fce..3e9095342 100644
--- a/app/models/tag_subscription.rb
+++ b/app/models/tag_subscription.rb
@@ -71,7 +71,7 @@ class TagSubscription < ActiveRecord::Base
     end
 
     if params[:creator_name]
-      q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].downcase)
+      q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].mb_chars.downcase)
     end
 
     q
@@ -113,7 +113,7 @@ class TagSubscription < ActiveRecord::Base
     relation = where("creator_id = ?", user_id)
 
     if name
-      relation = relation.where("lower(name) LIKE ? ESCAPE E'\\\\'", name.downcase.to_escaped_for_sql_like)
+      relation = relation.where("lower(name) LIKE ? ESCAPE E'\\\\'", name.mb_chars.downcase.to_escaped_for_sql_like)
     end
 
     relation.each do |tag_sub|
diff --git a/app/models/upload.rb b/app/models/upload.rb
index aa9c7e676..28fb80e8b 100644
--- a/app/models/upload.rb
+++ b/app/models/upload.rb
@@ -359,7 +359,7 @@ class Upload < ActiveRecord::Base
       end
 
       if params[:uploader_name].present?
-        q = q.where("uploader_id = (select _.id from users _ where lower(_.name) = ?)", params[:uploader_name].downcase)
+        q = q.where("uploader_id = (select _.id from users _ where lower(_.name) = ?)", params[:uploader_name].mb_chars.downcase)
       end
 
       if params[:source].present?
diff --git a/app/models/user_feedback.rb b/app/models/user_feedback.rb
index abf899f5c..85438b3b4 100644
--- a/app/models/user_feedback.rb
+++ b/app/models/user_feedback.rb
@@ -35,7 +35,7 @@ class UserFeedback < ActiveRecord::Base
       end
 
       if params[:user_name].present?
-        q = q.where("user_id = (select _.id from users _ where lower(_.name) = ?)", params[:user_name].downcase)
+        q = q.where("user_id = (select _.id from users _ where lower(_.name) = ?)", params[:user_name].mb_chars.downcase)
       end
 
       if params[:creator_id].present?
@@ -43,7 +43,7 @@ class UserFeedback < ActiveRecord::Base
       end
 
       if params[:creator_name].present?
-        q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].downcase)
+        q = q.where("creator_id = (select _.id from users _ where lower(_.name) = ?)", params[:creator_name].mb_chars.downcase)
       end
 
       q
diff --git a/app/models/wiki_page.rb b/app/models/wiki_page.rb
index b991b1dd5..a372545d6 100644
--- a/app/models/wiki_page.rb
+++ b/app/models/wiki_page.rb
@@ -14,7 +14,7 @@ class WikiPage < ActiveRecord::Base
 
   module SearchMethods
     def titled(title)
-      where("title = ?", title.downcase.tr(" ", "_"))
+      where("title = ?", title.mb_chars.downcase.tr(" ", "_"))
     end
 
     def recent
@@ -30,7 +30,7 @@ class WikiPage < ActiveRecord::Base
       params = {} if params.blank?
 
       if params[:title].present?
-        q = q.where("title LIKE ? ESCAPE E'\\\\'", params[:title].downcase.tr(" ", "_").to_escaped_for_sql_like)
+        q = q.where("title LIKE ? ESCAPE E'\\\\'", params[:title].mb_chars.downcase.tr(" ", "_").to_escaped_for_sql_like)
       end
 
       if params[:creator_id].present?
@@ -102,7 +102,7 @@ class WikiPage < ActiveRecord::Base
   end
 
   def normalize_title
-    self.title = title.downcase.tr(" ", "_")
+    self.title = title.mb_chars.downcase.tr(" ", "_")
   end
 
   def creator_name
@@ -156,6 +156,6 @@ class WikiPage < ActiveRecord::Base
       else
         match
       end
-    end.map {|x| x.downcase.tr(" ", "_")}
+    end.map {|x| x.mb_chars.downcase.tr(" ", "_")}
   end
 end