diff --git a/app/uat_actions/uat_actions/tube_submission.rb b/app/uat_actions/uat_actions/tube_submission.rb
index 190a640704..a4ec436b7f 100644
--- a/app/uat_actions/uat_actions/tube_submission.rb
+++ b/app/uat_actions/uat_actions/tube_submission.rb
@@ -122,6 +122,7 @@ def validate_submission_template_exists
   # @return [void]
   def validate_tubes_exist
     return if tube_barcodes.blank? # already validated by presence
+
     barcodes =
       tube_barcodes
         .gsub(/(\\[trfvn])+/, ' ')
@@ -130,6 +131,10 @@ def validate_tubes_exist
           Tube.find_by_barcode(barcode).blank? # not found
         end
 
+    # return if all tubes exist
+    return if barcodes.blank?
+
+    # add error message listing tubes that do not exist
     message = format(ERROR_TUBES_DO_NOT_EXIST, barcodes.join(', '))
     errors.add(:tube_barcodes, message)
   end