diff --git a/lib/fluent/plugin/in_s3.rb b/lib/fluent/plugin/in_s3.rb
index c270f53..1244b49 100644
--- a/lib/fluent/plugin/in_s3.rb
+++ b/lib/fluent/plugin/in_s3.rb
@@ -156,8 +156,8 @@ def start
           raise "#{bucket} is not found." unless @buckets[bucket].exists?
         end
       else
-        @buckets[bucket] = @s3.bucket(@s3_buckets)
-        raise "#{bucket} is not found." unless @buckets[bucket].exists?
+        @buckets[@s3_buckets] = @s3.bucket(@s3_buckets)
+        raise "#{@s3_buckets} is not found." unless @buckets[@s3_buckets].exists?
       end
 
       check_apikeys if @check_apikey_on_start
diff --git a/test/test_in_s3.rb b/test/test_in_s3.rb
index 01b2ecd..6995200 100644
--- a/test/test_in_s3.rb
+++ b/test/test_in_s3.rb
@@ -228,7 +228,7 @@ def setup_mocks
     mock(Aws::S3::Client).new(anything).at_least(0) { @s3_client }
     @s3_resource = mock(Aws::S3::Resource.new(client: @s3_client))
     mock(Aws::S3::Resource).new(client: @s3_client) { @s3_resource }
-    @s3_bucket = mock(Aws::S3::Bucket.new(name: "test",
+    @s3_bucket = mock(Aws::S3::Bucket.new(name: "test_bucket",
                                           client: @s3_client))
     @s3_bucket.exists? { true }
     @s3_resource.bucket(anything) { @s3_bucket }
@@ -278,6 +278,9 @@ def test_one_record
           "s3" => {
             "object" => {
               "key" => "test_key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -313,6 +316,9 @@ def test_one_record_with_metadata
           "s3" => {
             "object" => {
               "key" => "test_key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -348,6 +354,9 @@ def test_one_record_url_encoded
           "s3" => {
             "object" => {
               "key" => "test+key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -383,6 +392,9 @@ def test_one_record_url_encoded_with_metadata
           "s3" => {
             "object" => {
               "key" => "test+key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -418,6 +430,9 @@ def test_one_record_multi_line
           "s3" => {
             "object" => {
               "key" => "test_key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -458,6 +473,9 @@ def test_one_record_multi_line_with_metadata
           "s3" => {
             "object" => {
               "key" => "test_key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -506,6 +524,9 @@ def test_gzip_single_stream
           "s3" => {
             "object" => {
               "key" => "test_key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }
@@ -557,6 +578,9 @@ def test_gzip_multiple_steams
           "s3" => {
             "object" => {
               "key" => "test_key"
+            },
+            "bucket" => {
+              "name"=> "test_bucket"
             }
           }
         }