diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 0f44baa2feb4f1ea2f1984915c7e59d2caabcb58..b0e6136e12028673a60252d2202fccb673aa0b55 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -203,6 +203,10 @@ def rollback_to_savepoint
       def release_savepoint
       end
 
+      def case_sensitive_modifier(node)
+        node
+      end
+
       def current_savepoint_name
         "active_record_#{open_transactions}"
       end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index 7bad511c64937e36b380b70b3f1ae47575626aa4..7e237db35769c80a7a2d9209230adde03c0675ab 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -528,6 +528,11 @@ def primary_key(table)
       def case_sensitive_equality_operator
         "= BINARY"
       end
+      deprecate :case_sensitive_equality_operator
+
+      def case_sensitive_modifier(node)
+        Arel::Nodes::Bin.new(node)
+      end
 
       def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
         where_sql
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index e1186209d38c204b0fb3607e8b0d651886412217..ceee2ab73a4b6671351726f46cd01b1f23e50f95 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -655,6 +655,11 @@ def primary_key(table)
       def case_sensitive_equality_operator
         "= BINARY"
       end
+      deprecate :case_sensitive_equality_operator
+
+      def case_sensitive_modifier(node)
+        Arel::Nodes::Bin.new(node)
+      end
 
       def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
         where_sql
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 37381d063df0ffbb9f6ee24ec2ac468238870ae7..d1225a9ed959e8c0186fa2886510748f3f5b83a4 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -59,6 +59,7 @@ def build_relation(klass, table, attribute, value) #:nodoc:
         if !options[:case_sensitive] && column.text?
           relation = table[attribute].matches(value)
         else
+          value    = klass.connection.case_sensitive_modifier(value)
           relation = table[attribute].eq(value)
         end