diff --git a/app/models/fluentd/agent/local_common.rb b/app/models/fluentd/agent/local_common.rb
index 06f2f75..a9b7e1e 100644
--- a/app/models/fluentd/agent/local_common.rb
+++ b/app/models/fluentd/agent/local_common.rb
@@ -55,6 +55,7 @@ class Fluentd
 
       def pid
         return unless File.exists?(pid_file)
+        return if File.zero?(pid_file)
         File.read(pid_file).to_i rescue nil
       end
 
diff --git a/spec/models/fluentd/agent/local_common_spec.rb b/spec/models/fluentd/agent/local_common_spec.rb
index a928ce9..582804d 100644
--- a/spec/models/fluentd/agent/local_common_spec.rb
+++ b/spec/models/fluentd/agent/local_common_spec.rb
@@ -20,10 +20,10 @@ describe 'Fluentd::Agent::LocalCommon' do
     end
 
     context 'valid pid file given' do
-      before { File.write pid_file_path, '99999' }
+      before { File.write pid_file_path, '9999' }
       after  { FileUtils.rm pid_file_path }
 
-      its(:pid) { should eq(99999) }
+      its(:pid) { should eq(9999) }
     end
   end
 end