diff --git a/lib/morfo.rb b/lib/morfo.rb
index f6d20ff..e1cecc1 100644
--- a/lib/morfo.rb
+++ b/lib/morfo.rb
@@ -1,4 +1,4 @@
-require "active_support/core_ext/hash"
+require 'deep_merge/rails_compat'
 require "morfo/version"
 require "morfo/tools"
 require "morfo/actions"
@@ -20,7 +20,7 @@ def self.morf input, options = {}
     def self.morf_single input, options = {}
       output = {}
       mapping_actions.each do |field_path, action|
-        output.deep_merge!(store_value(action.execute(input), field_path, options))
+        output.deeper_merge!(store_value(action.execute(input), field_path, options))
       end
       output
     end
diff --git a/lib/morfo/builder.rb b/lib/morfo/builder.rb
index 42c8b90..e4ef994 100644
--- a/lib/morfo/builder.rb
+++ b/lib/morfo/builder.rb
@@ -7,7 +7,7 @@ def initialize(definitions)
     def build
       # WTF??? `definitions` is not accessible inside class
       # so this javascript technique is necesseray
-      tmp_definitions = definitions.map { |h| h.symbolize_keys }
+      tmp_definitions = definitions.map { |h| Morfo::Tools::ExtendedHash.symbolize_keys(h) }
       Class.new(Morfo::Base) do
         tmp_definitions.each do |definition|
           f = field(*definition[:field])
diff --git a/lib/morfo/tools.rb b/lib/morfo/tools.rb
index 1a7da3d..a68c67d 100644
--- a/lib/morfo/tools.rb
+++ b/lib/morfo/tools.rb
@@ -1,5 +1,22 @@
 module Morfo
   module Tools
+    module ExtendedHash
+      extend self
+
+      def symbolize_keys(hash)
+        transform_keys(hash) { |key| key.to_sym rescue key }
+      end
+
+      def transform_keys(hash)
+        return hash.enum_for(:transform_keys) { size } unless block_given?
+        result = {}
+        hash.each_key do |key|
+          result[yield(key)] = hash[key]
+        end
+        result
+      end
+    end
+
     class FlattenHashKeys
       attr_reader :input_hash
 
@@ -10,10 +27,10 @@ def initialize(input_hash)
       def flatten
         input_hash.inject({}) do |result_hash, (key, value)|
           inner_hash = false
-          if value.is_a?(Hash)
+          if value.is_a?(::Hash)
             inner_hash = true
             value.each do |inner_key, inner_value|
-              if inner_value.is_a?(Hash)
+              if inner_value.is_a?(::Hash)
                 inner_hash = true
               end
               result_hash.merge!("#{key}.#{inner_key}".to_sym => inner_value)
diff --git a/morfo.gemspec b/morfo.gemspec
index 53a83c3..c34a9b2 100644
--- a/morfo.gemspec
+++ b/morfo.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 2.0.0'
 
   spec.add_runtime_dependency "json"
-  spec.add_runtime_dependency "activesupport", "< 5.0"
+  spec.add_runtime_dependency "deep_merge"
   spec.add_runtime_dependency "rubysl" if RUBY_ENGINE == "rbx"
 
   spec.add_development_dependency "rake"