artifactId is not appended any more in distributionManagement.site.url in multi modules when it's not defined in a child

My root pom is :
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>maven</groupId>
<artifactId>p0</artifactId>
<packaging>pom</packaging>
<name>p0</name>
<version>1.0</version>
<modules>
<module>p1</module>
</modules>
<distributionManagement>
<site>
<id>distSiteId</id>
<url>sftp://ip/path/</url>
</site>
</distributionManagement>
</project>

My child pom doesn't have distributionManagement defined : the site is deployed to sftp://ip/path/ instead of sftp://ip/path/p1