diff --git a/lib/ldclient-rb/impl/integrations/file_data_source.rb b/lib/ldclient-rb/impl/integrations/file_data_source.rb
index 1e7ad078..8c62c909 100644
--- a/lib/ldclient-rb/impl/integrations/file_data_source.rb
+++ b/lib/ldclient-rb/impl/integrations/file_data_source.rb
@@ -35,6 +35,7 @@ def initialize(data_store, data_source_update_sink, logger, options={})
           if @paths.is_a? String
             @paths = [ @paths ]
           end
+          @allow_duplicates = options[:allow_duplicates] || false
           @auto_update = options[:auto_update]
           @use_listen = @auto_update && @@have_listen && !options[:force_polling]
           @poll_interval = options[:poll_interval] || 1
@@ -139,7 +140,7 @@ def add_item(all_data, kind, item)
           items = all_data[kind]
           raise ArgumentError, "Received unknown item kind #{kind[:namespace]} in add_data" if items.nil? # shouldn't be possible since we preinitialize the hash
           key = item[:key].to_sym
-          unless items[key].nil?
+          unless items[key].nil? || @allow_duplicates
             raise ArgumentError, "#{kind[:namespace]} key \"#{item[:key]}\" was used more than once"
           end
           items[key] = Model.deserialize(kind, item)
diff --git a/lib/ldclient-rb/integrations/file_data.rb b/lib/ldclient-rb/integrations/file_data.rb
index fb85ad98..36e847ca 100644
--- a/lib/ldclient-rb/integrations/file_data.rb
+++ b/lib/ldclient-rb/integrations/file_data.rb
@@ -97,6 +97,9 @@ module FileData
       # @option options [Float] :poll_interval  The minimum interval, in seconds, between checks for
       #   file modifications - used only if auto_update is true, and if the native file-watching
       #   mechanism from 'listen' is not being used. The default value is 1 second.
+      # @option options [Boolean] :allow_duplicates Do not raise an error if using multiple files
+      #   that contain the same flag or segment key. If this is true, the last value for a given key
+      #   will be used. The default is false.
       # @return an object that can be stored in {Config#data_source}
       #
       def self.data_source(options={})
diff --git a/spec/integrations/file_data_source_spec.rb b/spec/integrations/file_data_source_spec.rb
index 8b22e902..7fa6f5b8 100644
--- a/spec/integrations/file_data_source_spec.rb
+++ b/spec/integrations/file_data_source_spec.rb
@@ -37,6 +37,22 @@ module Integrations
 EOF
       }
 
+      let(:alternate_flag_only_json) { <<-EOF
+{
+  "flags": {
+    "flag1": {
+      "key": "flag1",
+      "on": false,
+      "fallthrough": {
+        "variation": 2
+      },
+      "variations": [ "fall", "off", "on" ]
+    }
+  }
+}
+EOF
+      }
+
       let(:segment_only_json) { <<-EOF
 {
   "segments": {
@@ -243,6 +259,17 @@ def with_data_source(options, initialize_to_valid = false)
         end
       end
 
+      it "allows duplicate keys and uses the last loaded version when allow-duplicates is true" do
+        file1 = make_temp_file(flag_only_json)
+        file2 = make_temp_file(alternate_flag_only_json)
+        with_data_source({ paths: [ file1.path, file2.path ], allow_duplicates: true }) do |ds|
+          ds.start
+          expect(@store.initialized?).to eq(true)
+          expect(@store.all(LaunchDarkly::FEATURES).keys).to_not eq([])
+          expect(@store.all(LaunchDarkly::FEATURES)[:flag1][:on]).to eq(false)
+        end
+      end
+
       it "does not reload modified file if auto-update is off" do
         file = make_temp_file(flag_only_json)