How do I properly add --add-opens to jvmArgs in JavaExec task

Currently I have a task that executes to run the program, something like

task runApp(type: JavaExec) {
    classpath = sourceSets.main.runtimeClasspath

    main = 'com.eonmux.somepackage'

    jvmArgs '-Xmx4096m'
}

I'm trying to add --add-opens to the list of JVM args so that I can allow reflection access from my gradle packages

Something like

task runApp(type: JavaExec) {
    classpath = sourceSets.main.runtimeClasspath

    main = 'com.eonmux.somepackage'

    jvmArgs '-Xmx4096m','--add-opens java.base/jdk.internal.loader=ALL-UNNAMED'
}

However this gives the following error saying that the command line option is unrecognized

2020-12-09T16:30:56.285-0500 [INFO] [org.gradle.process.internal.DefaultExecHandle] Successfully started process 'command 'C:\Program Files\AdoptOpenJDK\jdk-11.0.6.10-openj9\bin\java.exe''
2020-12-09T16:30:56.286-0500 [DEBUG] [org.gradle.process.internal.ExecHandleRunner] waiting until streams are handled...
2020-12-09T16:30:56.360-0500 [ERROR] [system.err] JVMJ9VM007E Command-line option unrecognised: --add-opens java.base/jdk.internal.loader=ALL-UNNAMED
2020-12-09T16:30:56.361-0500 [ERROR] [system.err] Error: Could not create the Java Virtual Machine.
Could not create the Java Virtual Machine.

2020-12-09T16:30:56.362-0500 [ERROR] [system.err] Error: A fatal exception has occurred. Program will exit.
A fatal exception has occurred. Program will exit.

Which is strange because when I open up a command line to the Java path indicated, and run

C:\Program Files\AdoptOpenJDK\jdk-11.0.6.10-openj9\bin>java --add-opens

I get the following message confirming its existence

Error: --add-opens requires modules to be specified

I'm no Gradle configuration expert, so I'd appreciate some help.

This is on Windows 10x64 with the IntelliJ IDE and Gradle 6.0.1