Error locating assembly descriptor: assembly.xml

Quando tento fazer o build o projeto está dando esse erro: Failed to execute goal org.apache.maven.plugins:maven-assembly-plugin:2.3:assembly (default) on project vraptor-produtos: Error reading assemblies: Error locating assembly descriptor: assembly.xml

No arquivo pom.xml tem essar parte desse plugin:

<plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.3</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <configuration>
                            <descriptors>
                                <descriptor>assembly.xml</descriptor>
                            </descriptors>
                        </configuration>
                        <goals>
                            <goal>assembly</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

Alguém sabe o que poderia ser?