Build error due to unsupported tag <tt> in generated javadoc in ECATokenLexer

ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.1.0:jar (javadoc-jar) on project byteman-agent: MavenReportException: Error while generating Javadoc:
[ERROR] Exit code: 1 - /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:37: error: tag not supported in the generated HTML version: tt
[ERROR] * <tt>/home/adinn/jboss/byteman/git/byteman/agent/grammar/flex/ECAToken.flex</tt>
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/agent/RuleScript.java:382: warning: no @param for rule
[ERROR] public synchronized boolean recordCompile(Rule rule, String triggerClass, ClassLoader loader, boolean successful, String detail)
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/agent/RuleScript.java:415: warning: no @param for loader
[ERROR] public synchronized void purge(ClassLoader loader, String triggerClassName)
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/agent/RuleScript.java:415: warning: no @param for triggerClassName
[ERROR] public synchronized void purge(ClassLoader loader, String triggerClassName)
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECAGrammarParser.java:21: warning: no @param for s
[ERROR] public ECAGrammarParser(java_cup.runtime.Scanner s)

{super(s);}

[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECAGrammarParser.java:24: warning: no @param for s
[ERROR] public ECAGrammarParser(java_cup.runtime.Scanner s, java_cup.runtime.SymbolFactory sf)

{super(s,sf);}
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECAGrammarParser.java:24: warning: no @param for sf
[ERROR] public ECAGrammarParser(java_cup.runtime.Scanner s, java_cup.runtime.SymbolFactory sf) {super(s,sf);}

[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:644: warning: no @throws for java.io.IOException
[ERROR] public final void yyclose() throws java.io.IOException {
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:659: error: tag not supported in the generated HTML version: tt
[ERROR] * Lexical state is set to <tt>ZZ_INITIAL</tt>.
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:678: warning: no @return
[ERROR] public final int yystate() {
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:696: warning: no @return
[ERROR] public final String yytext() {
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:702: error: tag not supported in the generated HTML version: tt
[ERROR] * Returns the character at position <tt>pos</tt> from the
[ERROR] ^
[ERROR] /home/opalka/git/redhat/PUBLIC/byteman/agent/src/main/java/org/jboss/byteman/rule/grammar/ECATokenLexer.java:720: warning: no @return
[ERROR] public final int yylength() {
[ERROR] ^
[ERROR]
[ERROR] Command line was: /home/opalka/java/jdk/oracle/11/latest/bin/javadoc @options @packages
[ERROR]
[ERROR] Refer to the generated Javadoc files in '/home/opalka/git/redhat/PUBLIC/byteman/agent/target/apidocs' dir.
[ERROR]
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR] mvn <args> -rf :byteman-agent