s3-fluent-parser error

gistfile1.txt

ito@ito:~/embulk$ embulk preview config/s3_fluent_load.yml 
2015-12-02 00:28:28.930 -0800: Embulk v0.7.1
2015-12-02 00:28:30.186 -0800 [INFO] (preview): Loaded plugin embulk-input-s3 (0.2.3)
2015-12-02 00:28:30.229 -0800 [INFO] (preview): Loaded plugin embulk-parser-fluent-s3-log (0.0.1)
java.lang.IllegalArgumentException: Multiple entries with same key: material_id=org.embulk.spi.util.dynamic.StringColumnSetter@5a82bc58 and material_id=org.embulk.spi.util.dynamic.StringColumnSetter@4aab7195
        at com.google.common.collect.ImmutableMap.checkNoConflict(com/google/common/collect/com/google/common/collect/com/google/common/collect/ImmutableMap.java:150)
        at com.google.common.collect.RegularImmutableMap.checkNoConflictInBucket(com/google/common/collect/com/google/common/collect/com/google/common/collect/RegularImmutableMap.java:104)
        at com.google.common.collect.RegularImmutableMap.<init>(com/google/common/collect/com/google/common/collect/com/google/common/collect/RegularImmutableMap.java:70)
        at com.google.common.collect.ImmutableMap$Builder.build(com/google/common/collect/com/google/common/collect/com/google/common/collect/ImmutableMap.java:254)
        at org.embulk.spi.util.DynamicPageBuilder.<init>(org/embulk/spi/util/org/embulk/spi/util/org/embulk/spi/util/DynamicPageBuilder.java:79)
        at java.lang.reflect.Constructor.newInstance(java/lang/reflect/java/lang/reflect/java/lang/reflect/Constructor.java:422)
        at RUBY.initialize(/home/ito/.embulk/bin/embulk!/embulk/page_builder.rb:11)
        at RUBY.run(/home/ito/.embulk/bin/embulk!/embulk/parser_plugin.rb:55)
        at Embulk$$ParserPlugin$$JavaAdapter_276593397.run(Embulk$$ParserPlugin$$JavaAdapter_276593397.gen:13)
        at org.embulk.spi.FileInputRunner.run(org/embulk/spi/org/embulk/spi/org/embulk/spi/FileInputRunner.java:147)
        at org.embulk.exec.PreviewExecutor$2$1.run(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:109)
        at org.embulk.spi.util.Filters$RecursiveControl.transaction(org/embulk/spi/util/org/embulk/spi/util/org/embulk/spi/util/Filters.java:96)
        at org.embulk.spi.util.Filters.transaction(org/embulk/spi/util/org/embulk/spi/util/org/embulk/spi/util/Filters.java:49)
        at org.embulk.exec.PreviewExecutor$2.run(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:96)
        at org.embulk.spi.FileInputRunner$RunnerControl$1$1.run(org/embulk/spi/org/embulk/spi/org/embulk/spi/FileInputRunner.java:118)
        at java.lang.reflect.Method.invoke(java/lang/reflect/java/lang/reflect/java/lang/reflect/Method.java:497)
        at RUBY.block in transaction(/home/ito/.embulk/bin/embulk!/embulk/parser_plugin.rb:46)
        at RUBY.transaction(/home/ito/.embulk/jruby/2.2.0/gems/embulk-parser-fluent-s3-log-0.0.1/lib/embulk/parser/fluent-s3-log.rb:20)
        at RUBY.transaction(/home/ito/.embulk/bin/embulk!/embulk/parser_plugin.rb:43)
        at Embulk$$ParserPlugin$$JavaAdapter_276593397.transaction(Embulk$$ParserPlugin$$JavaAdapter_276593397.gen:13)
        at org.embulk.spi.FileInputRunner$RunnerControl$1.run(org/embulk/spi/org/embulk/spi/org/embulk/spi/FileInputRunner.java:112)
        at org.embulk.spi.util.Decoders$RecursiveControl.transaction(org/embulk/spi/util/org/embulk/spi/util/org/embulk/spi/util/Decoders.java:77)
        at org.embulk.spi.util.Decoders.transaction(org/embulk/spi/util/org/embulk/spi/util/org/embulk/spi/util/Decoders.java:33)
        at org.embulk.spi.FileInputRunner$RunnerControl.run(org/embulk/spi/org/embulk/spi/org/embulk/spi/FileInputRunner.java:109)
        at org.embulk.input.s3.AbstractS3FileInputPlugin.resume(org/embulk/input/s3/org/embulk/input/s3/org/embulk/input/s3/AbstractS3FileInputPlugin.java:106)
        at org.embulk.input.s3.AbstractS3FileInputPlugin.transaction(org/embulk/input/s3/org/embulk/input/s3/org/embulk/input/s3/AbstractS3FileInputPlugin.java:93)
        at org.embulk.spi.FileInputRunner.transaction(org/embulk/spi/org/embulk/spi/org/embulk/spi/FileInputRunner.java:64)
        at org.embulk.exec.PreviewExecutor.doPreview(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:93)
        at org.embulk.exec.PreviewExecutor.access$000(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:27)
        at org.embulk.exec.PreviewExecutor$1.run(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:67)
        at org.embulk.exec.PreviewExecutor$1.run(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:63)
        at org.embulk.spi.Exec.doWith(org/embulk/spi/org/embulk/spi/org/embulk/spi/Exec.java:25)
        at org.embulk.exec.PreviewExecutor.preview(org/embulk/exec/org/embulk/exec/org/embulk/exec/PreviewExecutor.java:63)
        at org.embulk.EmbulkEmbed.preview(org/embulk/org/embulk/org/embulk/EmbulkEmbed.java:168)
        at java.lang.reflect.Method.invoke(java/lang/reflect/java/lang/reflect/java/lang/reflect/Method.java:497)
        at RUBY.preview(/home/ito/.embulk/bin/embulk!/embulk/runner.rb:35)
        at RUBY.run(/home/ito/.embulk/bin/embulk!/embulk/command/embulk_run.rb:272)
        at RUBY.<top>(/home/ito/.embulk/bin/embulk!/embulk/command/embulk_main.rb:2)
        at RUBY.(root)(uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:1)
        at home.ito.$_dot_embulk.bin.embulk.embulk.command.embulk_bundle.<top>(home/ito/$_dot_embulk/bin/embulk/embulk/command/home/ito/$_dot_embulk/bin/embulk/embulk/command/file:/home/ito/.embulk/bin/embulk!/e
mbulk/command/embulk_bundle.rb:55)
        at java.lang.invoke.MethodHandle.invokeWithArguments(java/lang/invoke/java/lang/invoke/java/lang/invoke/MethodHandle.java:625)
        at org.embulk.cli.Main.main(org/embulk/cli/org/embulk/cli/org/embulk/cli/Main.java:20)

Error: Multiple entries with same key: material_id=org.embulk.spi.util.dynamic.StringColumnSetter@5a82bc58 and material_id=org.embulk.spi.util.dynamic.StringColumnSetter@4aab7195
ito@ito:~/embulk$