"Invalid initial heap size" after any neo4j / neo4j-admin command

I'm setting up a new laptop for development, and I must have missed a step. My OS is Linux 4.19.28-1-MANJARO x86_64 GNU/Linux. I'm using OpenJDK8:

$ ⟩ java -version
openjdk version "1.8.0_202"
OpenJDK Runtime Environment (build 1.8.0_202-b26)
OpenJDK 64-Bit Server VM (build 25.202-b26, mixed mode)

The neo4j version is 3.5.3, although if I ask neo4j itself I get this bad news:

$ ⟩ neo4j --version
Invalid initial heap size: -Xms2048m
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

The neo4j.log reads in part

⟩ cat neo4j.log 
nohup: ignoring input
Invalid initial heap size: -Xms2048m
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
nohup: ignoring input
2019-03-19 19:44:41.600+0000 WARN  ha.pull_interval is deprecated.
2019-03-19 19:44:41.604+0000 WARN  dbms.security.procedures.roles is deprecated.
2019-03-19 19:44:41.615+0000 INFO  ======== Neo4j 3.5.3 ========
2019-03-19 19:44:41.618+0000 INFO  Starting...
2019-03-19 19:44:42.342+0000 ERROR Failed to start Neo4j: Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase@6b7906b3' was successfully initialized, but failed to start. Please see the attached cause exception "org.neo4j.kernel.impl.logging.LogService". Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase@6b7906b3' was successfully initialized, but failed to start. Please see the attached cause exception "org.neo4j.kernel.impl.logging.LogService".
org.neo4j.server.ServerStartupException: Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase@6b7906b3' was successfully initialized, but failed to start. Please see the attached cause exception "org.neo4j.kernel.impl.logging.LogService".
        at org.neo4j.server.exception.ServerStartupErrors.translateToServerStartupError(ServerStartupErrors.java:45)
        at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:184)
        at org.neo4j.server.ServerBootstrapper.start(ServerBootstrapper.java:123)
        at org.neo4j.server.ServerBootstrapper.start(ServerBootstrapper.java:90)
        at com.neo4j.server.enterprise.CommercialEntryPoint.main(CommercialEntryPoint.java:22)
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.server.database.LifecycleManagingDatabase@6b7906b3' was successfully initialized, but failed to start. Please see the attached cause exception "org.neo4j.kernel.impl.logging.LogService"...

(I'm omitting the rest because, surely it all depends on that heap error.) I am able to compile and run a HelloWorld.class in Java, and I'm able to start a Clojure 1.10 REPL, so I couldn't have messed up my JDK install that badly, I don't think. Are there environment variables I need to set up? Is there perhaps a Linux-specific neo4j.conf quirk that my Mac-using co-workers don't need to worry about? Something else entirely? Additional investigative steps would be most appreciated.

Turns out, this can be the result of running an apoc plugin that is not updated to the correct version! The heap was a red herring.