Jenkins global AWS credentials not working via `withAWS` step

I have a Jenkins v2.62 instance with the pipeline plugin installed and successfully usable. I have AWS credentials that are tested and working:

Now my pipeline job has something like this:

node("deploy-staging") {
    stage('test') {
        withEnv(["AWS_ACCESS_KEY_ID=${env.AWS_ACCESS_KEY_ID}",
                 "AWS_SECRET_ACCESS_KEY=${env.AWS_SECRET_ACCESS_KEY}",
                 "AWS_DEFAULT_REGION=${env.AWS_DEFAULT_REGION}"]) {
            // WORKS
            s3put -b my-bucket -k foo -p `pwd` text.txt
        }

        withAWS(credentials:'jenkins') {
            // DOES NOT WORK!
            s3Upload bucket: "my-bucket", path: "foo/text.txt"
        }

        echo "Done."
    }
}

I verified that the withEnv block works (because the Jenkins instance is configured with those three env variables globally set), but the withAWS block does not for some reason that I'm unable to figure out. I checked that there are no spaces in the name jenkins. The job hits this error:

java.lang.RuntimeException: Cannot find Jenkins credentials with name jenkins
    at de.taimos.pipeline.aws.WithAWSStep$Execution.withCredentials(WithAWSStep.java:179)
    at de.taimos.pipeline.aws.WithAWSStep$Execution.start(WithAWSStep.java:151)
    at org.jenkinsci.plugins.workflow.cps.DSL.invokeStep(DSL.java:184)
    at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:126)
    at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:108)
    at groovy.lang.GroovyObject$invokeMethod$47.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
    at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:151)
    at org.kohsuke.groovy.sandbox.GroovyInterceptor.onMethodCall(GroovyInterceptor.java:21)
    at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:115)
    at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:149)
    at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:146)
    at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:123)
    at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:123)
    at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:16)
    at WorkflowScript.run(WorkflowScript:26)
    at ___cps.transform___(Native Method)
    at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:57)
    at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:109)
    at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:82)
    at sun.reflect.GeneratedMethodAccessor402.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
    at com.cloudbees.groovy.cps.impl.ClosureBlock.eval(ClosureBlock.java:46)
    at com.cloudbees.groovy.cps.Next.step(Next.java:74)
    at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:154)
    at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:18)
    at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:33)
    at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:30)
    at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
    at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:30)
    at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:165)
    at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:330)
    at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$100(CpsThreadGroup.java:82)
    at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:242)
    at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:230)
    at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:112)
    at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Finished: FAILURE

The withAWS step appears to come from plugin of which I have version 1.7 installed.

Help!