Oozie job weird error : No input path Specified

Today I debugged with a couple guys on a strange oozie error. The MapRed job with error
"No input path Specified"
But we have the input dir set up in configuration and workflow.
It turned out to be that we missed two configurations for oozie job to tell oozie use the new api :

<property>
                    <name>mapred.mapper.new-api</name>
                    <value>true</value>
                </property>
                <property>
                    <name>mapred.reducer.new-api</name>
                    <value>true</value>
                </property>