diff --git a/lib/active_record/connection_adapters/oracle_enhanced/quoting.rb b/lib/active_record/connection_adapters/oracle_enhanced/quoting.rb
index 66175fcb2..c77b27df4 100644
--- a/lib/active_record/connection_adapters/oracle_enhanced/quoting.rb
+++ b/lib/active_record/connection_adapters/oracle_enhanced/quoting.rb
@@ -7,10 +7,12 @@ module Quoting
         # QUOTING ==================================================
         #
         # see: abstract/quoting.rb
+        QUOTED_COLUMN_NAMES = Concurrent::Map.new # :nodoc:
+        QUOTED_TABLE_NAMES = Concurrent::Map.new # :nodoc:
 
         def quote_column_name(name) # :nodoc:
           name = name.to_s
-          self.class.quoted_column_names[name] ||= if /\A[a-z][a-z_0-9$#]*\Z/.match?(name)
+          QUOTED_COLUMN_NAMES[name] ||= if /\A[a-z][a-z_0-9$#]*\Z/.match?(name)
             "\"#{name.upcase}\""
           else
             # remove double quotes which cannot be used inside quoted identifier
@@ -26,7 +28,7 @@ def quote_column_name_or_expression(name) # :nodoc:
           # if only valid lowercase column characters in name
           when /^[a-z][a-z_0-9$#]*$/
             "\"#{name.upcase}\""
-          when /^[a-z][a-z_0-9$#\-]*$/i
+          when /^[a-z][a-z_0-9$#-]*$/i
             "\"#{name}\""
           # if other characters present then assume that it is expression
           # which should not be quoted
@@ -67,7 +69,7 @@ def self.mixed_case?(name)
 
         def quote_table_name(name) # :nodoc:
           name, _link = name.to_s.split("@")
-          self.class.quoted_table_names[name] ||= [name.split(".").map { |n| quote_column_name(n) }].join(".")
+          QUOTED_TABLE_NAMES[name] ||= [name.split(".").map { |n| quote_column_name(n) }].join(".")
         end
 
         def quote_string(s) # :nodoc:
diff --git a/spec/active_record/oracle_enhanced/type/custom_spec.rb b/spec/active_record/oracle_enhanced/type/custom_spec.rb
index e7e50a84c..bcc04feda 100644
--- a/spec/active_record/oracle_enhanced/type/custom_spec.rb
+++ b/spec/active_record/oracle_enhanced/type/custom_spec.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "base64"
+
 describe "OracleEnhancedAdapter custom types handling" do
   include SchemaSpecHelper