diff --git a/app/builders/messages/message_builder.rb b/app/builders/messages/message_builder.rb
index 7d34af469..cff65e8f0 100644
--- a/app/builders/messages/message_builder.rb
+++ b/app/builders/messages/message_builder.rb
@@ -79,12 +79,20 @@ class Messages::MessageBuilder
     end
   end
 
-  def process_metadata(attachment)
+  def process_metadata(attachment) # rubocop:disable Metrics/CyclomaticComplexity,Metrics/PerceivedComplexity
     # NOTE: `is_recorded_audio` can be either a boolean or an array of file names.
     return unless @is_recorded_audio
     return { is_recorded_audio: true } if @is_recorded_audio == true
 
-    { is_recorded_audio: true } if @is_recorded_audio.is_a?(Array) && attachment.original_filename.in?(@is_recorded_audio)
+    return { is_recorded_audio: true } if @is_recorded_audio.is_a?(Array) && attachment.original_filename.in?(@is_recorded_audio)
+
+    # FIXME: Remove backwards compatibility with old format.
+    if @is_recorded_audio.is_a?(String)
+      parsed = JSON.parse(@is_recorded_audio)
+      { is_recorded_audio: true } if parsed.is_a?(Array) && attachment.original_filename.in?(parsed)
+    end
+  rescue JSON::ParserError
+    nil
   end
 
   def process_emails
diff --git a/app/javascript/dashboard/api/inbox/message.js b/app/javascript/dashboard/api/inbox/message.js
index 80534524e..903e5849c 100644
--- a/app/javascript/dashboard/api/inbox/message.js
+++ b/app/javascript/dashboard/api/inbox/message.js
@@ -23,7 +23,9 @@ export const buildCreatePayload = ({
     files.forEach(file => {
       payload.append('attachments[]', file);
     });
-    payload.append('is_recorded_audio', JSON.stringify(isRecordedAudio));
+    isRecordedAudio?.forEach(filename => {
+      payload.append('is_recorded_audio[]', filename);
+    });
     payload.append('private', isPrivate);
     payload.append('echo_id', echoId);
     payload.append('cc_emails', ccEmails);
diff --git a/spec/builders/messages/message_builder_spec.rb b/spec/builders/messages/message_builder_spec.rb
index aab3e2a09..ed0f16eaf 100644
--- a/spec/builders/messages/message_builder_spec.rb
+++ b/spec/builders/messages/message_builder_spec.rb
@@ -135,6 +135,14 @@ describe Messages::MessageBuilder do
       end
 
       it 'creates attachment with is_recorded_audio metadata' do
+        params[:is_recorded_audio] = true
+
+        message = message_builder
+
+        expect(message.attachments.first.meta).to eq({ 'is_recorded_audio' => true })
+      end
+
+      it 'creates attachment with is_recorded_audio metadata when param is array of filenames' do
         params[:is_recorded_audio] = ['avatar.png']
 
         message = message_builder
@@ -142,6 +150,14 @@ describe Messages::MessageBuilder do
         expect(message.attachments.first.meta).to eq({ 'is_recorded_audio' => true })
       end
 
+      it 'creates attachment with is_recorded_audio metadata when param is string with array' do
+        params[:is_recorded_audio] = '["avatar.png"]'
+
+        message = message_builder
+
+        expect(message.attachments.first.meta).to eq({ 'is_recorded_audio' => true })
+      end
+
       context 'when DIRECT_UPLOAD_ENABLED' do
         let(:params) do
           ActionController::Parameters.new({