I have a Docker file with the following COPY command:
COPY bin/server.crt bin/server.key /etc/httpd/ssl/

I get the following exception on build:
_ERROR: Build step failed with exception
java.lang.RuntimeException: java.lang.ClassCastException: org.glassfish.json.JsonObjectBuilderImpl$JsonObjectImpl cannot be cast to javax.json.JsonString
at org.jenkinsci.plugins.dockerbuildstep.cmd.CreateImageCommand.execute(CreateImageCommand.java:139)
at org.jenkinsci.plugins.dockerbuildstep.DockerBuilder.perform(DockerBuilder.java:75)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:779)
at hudson.model.Build$BuildExecution.build(Build.java:205)
at hudson.model.Build$BuildExecution.doRun(Build.java:162)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:534)
at hudson.model.Run.execute(Run.java:1720)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:404)
Caused by: java.lang.ClassCastException: org.glassfish.json.JsonObjectBuilderImpl$JsonObjectImpl cannot be cast to javax.json.JsonString
at org.glassfish.json.JsonObjectBuilderImpl$JsonObjectImpl.getJsonString(JsonObjectBuilderImpl.java:194)
at org.glassfish.json.JsonObjectBuilderImpl$JsonObjectImpl.getString(JsonObjectBuilderImpl.java:199)
at org.jenkinsci.plugins.dockerbuildstep.cmd.CreateImageCommand$1.callback(CreateImageCommand.java:123)
at org.jenkinsci.plugins.dockerbuildstep.cmd.CreateImageCommand.readJsonStream(CreateImageCommand.java:161)
at org.jenkinsci.plugins.dockerbuildstep.cmd.CreateImageCommand.execute(CreateImageCommand.java:115)
... 10 more
Build step 'Execute Docker command' marked build as failure
Finished: FAILURE_

If I split the COPY into 2 separate commands then it works fine.