"error: Unmet build dependencies: maven default-jdk (>= 2:1.8)" when running dpkg-buildpackage

[Steinar Bang <sb@dod.no>]

Build system configuration: debian 10.2 "buster", amd64
	                    openjdk-11-jdk 11.0.5+10-1~deb10u1
                            openjdk-8-jdk 8u222-b10-1~deb9u1
                            apache maven 3.6.2 (installed from tar-ball, not from deb package)

I'm trying to build karaf 4.2.7 using my karaf debian package project,
 https://github.com/steinarb/karaf-debian
but I get errors when running dpkg-build package:
 sb@lorenzo:~/git/karaf-debian$ dpkg-buildpackage
 dpkg-buildpackage: info: source package apache-karaf
 dpkg-buildpackage: info: source version 0-0
 dpkg-buildpackage: info: source distribution UNRELEASED
 dpkg-buildpackage: info: source changed by Steinar Bang <sb@dod.no>
 dpkg-buildpackage: info: host architecture amd64
  dpkg-source --before-build .
 dpkg-checkbuilddeps: error: Unmet build dependencies: maven default-jdk (>= 2:1.8)
 dpkg-buildpackage: warning: build dependencies/conflicts unsatisfied; aborting
 dpkg-buildpackage: warning: (Use -d flag to override.)
 sb@lorenzo:~/git/karaf-debian$

I have tried the following:
 1. Switching to openjdk-8 as the default JDK
 2. Set JAVA_HOME pointing to /usr/lib/jvm/java-8-openjdk-amd64
 3. Removing JAVA_HOME and switching back to opendjdk-11 as the default JDK 

But they all make dpkg-buildpackage fail with the same error.

Does anyone know what's the underlying error?

Thanks!