maven ignores maven.compiler.source - maven

Question

I have
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
in my pom.xml.
If I run mvn clean install then I can't run the compiled classes with Java 1.8 (I get crashes with errors like java.lang.NoClassDefFoundError: Could not initialize class when I try to).
I am forced to run
JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home mvn clean install
if I want it to be able to run the built jar with java 8 without crashes.
How can I make it actually use the correct JDK that I want?
Here is how my machine seems to be set up by default
$ mvn -version
Apache Maven 3.6.0 (97c98ec64a1fdfee7767ce5ffb20918da4f719f3; 2018-10-24T19:41:47+01:00)
Maven home: /usr/local/Cellar/maven/3.6.0/libexec
Java version: 11.0.1, vendor: Oracle Corporation, runtime: /Library/Java/JavaVirtualMachines/openjdk-11.0.1.jdk/Contents/Home
Default locale: en_GB, platform encoding: UTF-8
OS name: "mac os x", version: "10.14.2", arch: "x86_64", family: "mac"
$ java -version
openjdk version "11.0.1" 2018-10-16
OpenJDK Runtime Environment 18.9 (build 11.0.1+13)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.1+13, mixed mode)
$ echo $JAVA_HOME
$