diff --git a/lib/logstash/inputs/s3.rb b/lib/logstash/inputs/s3.rb
index 36a1f65..8bf3fe1 100644
--- a/lib/logstash/inputs/s3.rb
+++ b/lib/logstash/inputs/s3.rb
@@ -376,18 +376,22 @@ def ignore_filename?(filename)
   def process_log(queue, log)
     @logger.debug("Processing", :bucket => @bucket, :key => log.key)
     object = @s3bucket.object(log.key)
+    # Eager-loads the object data so the last_modified field is populated right before the download
+    object.load
 
     filename = File.join(temporary_directory, File.basename(log.key))
     if download_remote_file(object, filename)
       if process_local_log(queue, filename, object)
-        if object.last_modified == log.last_modified
+        refreshed_object = @s3bucket.object(log.key)
+        # If the object was modified during download and processing, do not backup/delete it and process it again during the next iteration
+        if object.last_modified == refreshed_object.last_modified
           backup_to_bucket(object)
           backup_to_dir(filename)
           delete_file_from_bucket(object)
           FileUtils.remove_entry_secure(filename, true)
-          sincedb.write(log.last_modified)
+          sincedb.write(object.last_modified)
         else
-          @logger.info("#{log.key} is updated at #{object.last_modified} and will process in the next cycle")
+          @logger.info("#{log.key} was updated at #{refreshed_object.last_modified} and will process in the next cycle")
         end
       end
     else
diff --git a/spec/inputs/s3_spec.rb b/spec/inputs/s3_spec.rb
index b34b682..beaee8f 100644
--- a/spec/inputs/s3_spec.rb
+++ b/spec/inputs/s3_spec.rb
@@ -32,6 +32,7 @@
     FileUtils.mkdir_p(sincedb_path)
     Aws.config[:stub_responses] = true
     Thread.abort_on_exception = true
+    allow_any_instance_of(Aws::S3::Object).to receive(:load)
   end
 
   context "when interrupting the plugin" do
@@ -583,7 +584,7 @@
       end
     end
 
-    context 's3 object updated after getting summary' do
+    context 's3 object updated during processing' do
       it 'should not update sincedb' do
         s3_summary = [
           double(:key => 'YESTERDAY', :last_modified => Time.now.round - day, :content_length => 5, :storage_class => 'STANDARD'),
@@ -592,6 +593,8 @@
 
         s3_objects = [
           double(:key => 'YESTERDAY', :last_modified => Time.now.round - day, :content_length => 5, :storage_class => 'STANDARD'),
+          double(:key => 'YESTERDAY', :last_modified => Time.now.round - day, :content_length => 5, :storage_class => 'STANDARD'),
+          double(:key => 'TODAY', :last_modified => Time.now.round - (cutoff * 10), :content_length => 5, :storage_class => 'STANDARD'),
           double(:key => 'TODAY_UPDATED', :last_modified => Time.now.round, :content_length => 5, :storage_class => 'STANDARD')
         ]