Maven run tests even with -DskipTests

I'm trying to skip tests when building a maven project. Here is the maven command:

mvn clean install -DskipTests -X

And I get the following output:

Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-test of goal org.apache.maven.plugins:maven-surefire-plugin:2.18.1:test failed: A required class was missing while executing org.apache.maven.plugins:maven-surefire-plugin:2.18.1:test: org/apache/maven/surefire/testset/TestSetFailedException

Can anybody give me any hint on where should I look for this issue?