diff --git a/fluent-plugin-google-cloud.gemspec b/fluent-plugin-google-cloud.gemspec
index c4e4ba5e..f81f817b 100644
--- a/fluent-plugin-google-cloud.gemspec
+++ b/fluent-plugin-google-cloud.gemspec
@@ -24,7 +24,7 @@ eos
   gem.add_runtime_dependency 'googleauth', '0.9.0'
   gem.add_runtime_dependency 'google-api-client', '0.30.8'
   gem.add_runtime_dependency 'google-cloud-logging', '1.6.6'
-  gem.add_runtime_dependency 'google-protobuf', '3.14.0'
+  gem.add_runtime_dependency 'google-protobuf', '3.15.8'
   gem.add_runtime_dependency 'grpc', '1.31.1'
   gem.add_runtime_dependency 'json', '2.2.0'
   gem.add_runtime_dependency 'opencensus', '0.5.0'
diff --git a/test/plugin/test_out_google_cloud_grpc.rb b/test/plugin/test_out_google_cloud_grpc.rb
index 2c66e20d..e1391f87 100644
--- a/test/plugin/test_out_google_cloud_grpc.rb
+++ b/test/plugin/test_out_google_cloud_grpc.rb
@@ -271,19 +271,19 @@ def latency_conversion
     {
       '32 s' => '32s',
       '32s' => '32s',
-      '0.32s' => '0.320000000s',
+      '0.32s' => '0.320s',
       ' 123 s ' => '123s',
-      '1.3442 s' => '1.344200000s',
+      '1.3442 s' => '1.344200s',
 
       # Test whitespace.
       # \t: tab. \r: carriage return. \n: line break.
       # \v: vertical whitespace. \f: form feed.
-      "\t123.5\ts\t" => '123.500000000s',
-      "\r123.5\rs\r" => '123.500000000s',
-      "\n123.5\ns\n" => '123.500000000s',
-      "\v123.5\vs\v" => '123.500000000s',
-      "\f123.5\fs\f" => '123.500000000s',
-      "\r123.5\ts\f" => '123.500000000s'
+      "\t123.5\ts\t" => '123.500s',
+      "\r123.5\rs\r" => '123.500s',
+      "\n123.5\ns\n" => '123.500s',
+      "\v123.5\vs\v" => '123.500s',
+      "\f123.5\fs\f" => '123.500s',
+      "\r123.5\ts\f" => '123.500s'
     }
   end