Setting cache.dir throws exception

[johndevs]

Calling

lazybones config set cache.dir '/tmp'

throws

Exception in thread "main" java.lang.ClassCastException: class [B cannot be cast to class [C ([B and [C are in module java.base of loader 'bootstrap')
        at groovy.json.internal.FastStringUtils$StringImplementation$1.toCharArray(FastStringUtils.java:89)
        at groovy.json.internal.FastStringUtils.toCharArray(FastStringUtils.java:174)
        at groovy.json.internal.CharBuf.addJsonFieldName(CharBuf.java:515)
        at groovy.json.JsonOutput.writeMap(JsonOutput.java:420)
        at groovy.json.JsonOutput.writeObject(JsonOutput.java:264)
        at groovy.json.JsonOutput.toJson(JsonOutput.java:184)
        at groovy.json.JsonBuilder.toString(JsonBuilder.java:322)
        at groovy.json.JsonBuilder.toPrettyString(JsonBuilder.java:336)
        at groovy.json.JsonBuilder$toPrettyString.call(Unknown Source)
        at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:110)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:114)
        at uk.co.cacoethes.lazybones.config.Configuration.storeSettings(Configuration.groovy:121)
        at uk.co.cacoethes.lazybones.config.Configuration$storeSettings$7.call(Unknown Source)
        at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:110)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:114)
        at uk.co.cacoethes.lazybones.commands.ConfigCommand.configSet(ConfigCommand.groovy:142)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:207)
        at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:56)
        at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:151)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:163)
        at uk.co.cacoethes.lazybones.commands.ConfigCommand.doExecute(ConfigCommand.groovy:85)
        at uk.co.cacoethes.lazybones.commands.AbstractCommand.execute(AbstractCommand.groovy:30)
        at uk.co.cacoethes.lazybones.LazybonesMain.main(LazybonesMain.groovy:89)