diff --git a/lib/fluent/plugin/output.rb b/lib/fluent/plugin/output.rb
index 7e3b6daad9..65d25e7201 100644
--- a/lib/fluent/plugin/output.rb
+++ b/lib/fluent/plugin/output.rb
@@ -589,13 +589,13 @@ def validate_time!
           example = @argument[:example]
           timekey = @argument[:timekey]
           if !sec && timekey
-            raise Fluent::ConfigError, "Parameter '#{name}' doesn't have timestamp placeholders for timekey #{timekey.to_i}"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' doesn't have timestamp placeholders for timekey #{timekey.to_i}"
           end
           if sec && !timekey
-            raise Fluent::ConfigError, "Parameter '#{name}' has timestamp placeholders, but chunk key 'time' is not configured"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' has timestamp placeholders, but chunk key 'time' is not configured"
           end
           if sec && timekey && timekey < sec
-            raise Fluent::ConfigError, "Parameter '#{@name}' doesn't have timestamp placeholder for #{title}('#{example}') for timekey #{timekey.to_i}"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' doesn't have timestamp placeholder for #{title}('#{example}') for timekey #{timekey.to_i}"
           end
         end
 
@@ -603,10 +603,10 @@ def validate_tag!
           parts = @argument[:parts]
           tagkey = @argument[:tagkey]
           if tagkey && parts.empty?
-            raise Fluent::ConfigError, "Parameter '#{@name}' doesn't have tag placeholder"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' doesn't have tag placeholder"
           end
           if !tagkey && !parts.empty?
-            raise Fluent::ConfigError, "Parameter '#{@name}' has tag placeholders, but chunk key 'tag' is not configured"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' has tag placeholders, but chunk key 'tag' is not configured"
           end
         end
 
@@ -615,11 +615,11 @@ def validate_keys!
           chunk_keys = @argument[:chunkkeys]
           if (chunk_keys - keys).size > 0
             not_specified = (chunk_keys - keys).sort
-            raise Fluent::ConfigError, "Parameter '#{@name}' doesn't have enough placeholders for keys #{not_specified.join(',')}"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' doesn't have enough placeholders for keys #{not_specified.join(',')}"
           end
           if (keys - chunk_keys).size > 0
             not_satisfied = (keys - chunk_keys).sort
-            raise Fluent::ConfigError, "Parameter '#{@name}' has placeholders, but chunk keys doesn't have keys #{not_satisfied.join(',')}"
+            raise Fluent::ConfigError, "Parameter '#{name}: #{string}' has placeholders, but chunk keys doesn't have keys #{not_satisfied.join(',')}"
           end
         end
       end
diff --git a/test/plugin/test_output.rb b/test/plugin/test_output.rb
index 57dd3376fc..73141b8281 100644
--- a/test/plugin/test_output.rb
+++ b/test/plugin/test_output.rb
@@ -315,7 +315,7 @@ def waiting(seconds)
         validators = @i.placeholder_validators(:path, "/my/path/file.%Y-%m-%d.log")
         assert_equal 1, validators.size
         assert_equal 1, validators.select(&:time?).size
-        assert_raise Fluent::ConfigError.new("Parameter 'path' has timestamp placeholders, but chunk key 'time' is not configured") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.%Y-%m-%d.log' has timestamp placeholders, but chunk key 'time' is not configured") do
           validators.first.validate!
         end
       end
@@ -325,7 +325,7 @@ def waiting(seconds)
         validators = @i.placeholder_validators(:path, "/my/path/to/file.log")
         assert_equal 1, validators.size
         assert_equal 1, validators.select(&:time?).size
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have timestamp placeholders for timekey 30") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/to/file.log' doesn't have timestamp placeholders for timekey 30") do
           validators.first.validate!
         end
       end
@@ -335,7 +335,7 @@ def waiting(seconds)
         validators = @i.placeholder_validators(:path, "/my/path/${tag}/file.log")
         assert_equal 1, validators.size
         assert_equal 1, validators.select(&:tag?).size
-        assert_raise Fluent::ConfigError.new("Parameter 'path' has tag placeholders, but chunk key 'tag' is not configured") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/${tag}/file.log' has tag placeholders, but chunk key 'tag' is not configured") do
           validators.first.validate!
         end
       end
@@ -345,7 +345,7 @@ def waiting(seconds)
         validators = @i.placeholder_validators(:path, "/my/path/file.log")
         assert_equal 1, validators.size
         assert_equal 1, validators.select(&:tag?).size
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have tag placeholder") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.log' doesn't have tag placeholder") do
           validators.first.validate!
         end
       end
@@ -355,7 +355,7 @@ def waiting(seconds)
         validators = @i.placeholder_validators(:path, "/my/path/${username}/file.${group}.log")
         assert_equal 1, validators.size
         assert_equal 1, validators.select(&:keys?).size
-        assert_raise Fluent::ConfigError.new("Parameter 'path' has placeholders, but chunk keys doesn't have keys group,username") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/${username}/file.${group}.log' has placeholders, but chunk keys doesn't have keys group,username") do
           validators.first.validate!
         end
       end
@@ -365,7 +365,7 @@ def waiting(seconds)
         validators = @i.placeholder_validators(:path, "/my/path/file.log")
         assert_equal 1, validators.size
         assert_equal 1, validators.select(&:keys?).size
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have enough placeholders for keys group,username") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.log' doesn't have enough placeholders for keys group,username") do
           validators.first.validate!
         end
       end
@@ -374,14 +374,14 @@ def waiting(seconds)
     sub_test_case '#placeholder_validate!' do
       test 'raises configuration error for a templace when timestamp placeholders exist but time key is missing' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', '')]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' has timestamp placeholders, but chunk key 'time' is not configured") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /path/without/timestamp/file.%Y%m%d-%H%M.log' has timestamp placeholders, but chunk key 'time' is not configured") do
           @i.placeholder_validate!(:path, "/path/without/timestamp/file.%Y%m%d-%H%M.log")
         end
       end
 
       test 'raises configuration error for a template without timestamp placeholders when timekey is configured' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', 'time', {"timekey" => 180})]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have timestamp placeholders for timekey 180") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.log' doesn't have timestamp placeholders for timekey 180") do
           @i.placeholder_validate!(:path, "/my/path/file.log")
         end
         assert_nothing_raised do
@@ -391,7 +391,7 @@ def waiting(seconds)
 
       test 'raises configuration error for a template with timestamp placeholders when plugin is configured more fine timekey' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', 'time', {"timekey" => 180})]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have timestamp placeholder for hour('%H') for timekey 180") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.%Y%m%d_%H.log' doesn't have timestamp placeholder for hour('%H') for timekey 180") do
           @i.placeholder_validate!(:path, "/my/path/file.%Y%m%d_%H.log")
         end
         assert_nothing_raised do
@@ -401,14 +401,14 @@ def waiting(seconds)
 
       test 'raises configuration error for a template when tag placeholders exist but tag key is missing' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', '')]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' has tag placeholders, but chunk key 'tag' is not configured") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/${tag}/file.${tag[2]}.log' has tag placeholders, but chunk key 'tag' is not configured") do
           @i.placeholder_validate!(:path, "/my/path/${tag}/file.${tag[2]}.log")
         end
       end
 
       test 'raises configuration error for a template without tag placeholders when tagkey is configured' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', 'tag')]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have tag placeholder") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.log' doesn't have tag placeholder") do
           @i.placeholder_validate!(:path, "/my/path/file.log")
         end
         assert_nothing_raised do
@@ -418,14 +418,14 @@ def waiting(seconds)
 
       test 'raises configuration error for a template when variable key placeholders exist but chunk keys are missing' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', '')]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' has placeholders, but chunk keys doesn't have keys service,username") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/${service}/file.${username}.log' has placeholders, but chunk keys doesn't have keys service,username") do
           @i.placeholder_validate!(:path, "/my/path/${service}/file.${username}.log")
         end
       end
 
       test 'raises configuration error for a template without variable key placeholders when chunk keys are configured' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', 'username,service')]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have enough placeholders for keys service,username") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.log' doesn't have enough placeholders for keys service,username") do
           @i.placeholder_validate!(:path, "/my/path/file.log")
         end
         assert_nothing_raised do
@@ -435,10 +435,10 @@ def waiting(seconds)
 
       test 'raise configuration error for a template and configuration with keys mismatch' do
         @i.configure(config_element('ROOT', '', {}, [config_element('buffer', 'username,service')]))
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have enough placeholders for keys service") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/file.${username}.log' doesn't have enough placeholders for keys service") do
           @i.placeholder_validate!(:path, "/my/path/file.${username}.log")
         end
-        assert_raise Fluent::ConfigError.new("Parameter 'path' doesn't have enough placeholders for keys username") do
+        assert_raise Fluent::ConfigError.new("Parameter 'path: /my/path/${service}/file.log' doesn't have enough placeholders for keys username") do
           @i.placeholder_validate!(:path, "/my/path/${service}/file.log")
         end
         assert_nothing_raised do