# ExecutionQueue	Uncaught Throwable during execution

**URL:** <https://forum.inductiveautomation.com/t/executionqueue-uncaught-throwable-during-execution/11150>\
**Category:** Ignition\
**Created:** [January 31, 2016, 10:37pm UTC](https://forum.inductiveautomation.com/t/executionqueue-uncaught-throwable-during-execution/11150 "2016-01-31T22:37:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jreynolds](https://avatars.discourse-cdn.com/v4/letter/j/58956e/32.png) [@jreynolds](https://forum.inductiveautomation.com/u/jreynolds)\
**Post date:** [January 31, 2016, 10:37pm UTC](https://forum.inductiveautomation.com/t/executionqueue-uncaught-throwable-during-execution/11150/1 "2016-01-31T22:37:16Z")

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I’m running a new SFC and trying to wirte to a PLC. I can write to memory tags, but when I try to write to a PLC tag i ge this error

`	
com.digitalpetri.opcua.stack.core.UaSerializationException: unknown builtin type: -1
at com.digitalpetri.opcua.stack.core.serialization.binary.BinaryEncoder.encodeBuiltinType(BinaryEncoder.java:758)
at com.digitalpetri.opcua.stack.core.serialization.binary.BinaryEncoder.encodeVariant(BinaryEncoder.java:594)
at com.digitalpetri.opcua.stack.core.serialization.binary.BinaryEncoder.encodeDataValue(BinaryEncoder.java:508)
at com.digitalpetri.opcua.stack.core.types.structured.WriteValue.encode(WriteValue.java:91)
at com.digitalpetri.opcua.stack.core.types.structured.WriteValue$$Lambda$445/2026473198.encode(Unknown Source)
at com.digitalpetri.opcua.stack.core.serialization.binary.BinaryEncoder.encodeSerializable(BinaryEncoder.java:660)
at com.digitalpetri.opcua.stack.core.types.structured.WriteRequest$$Lambda$679/1756538821.accept(Unknown Source)
at com.digitalpetri.opcua.stack.core.serialization.binary.BinaryEncoder.encodeArray(BinaryEncoder.java:675)
at com.digitalpetri.opcua.stack.core.types.structured.WriteRequest.encode(WriteRequest.java:73)
at com.digitalpetri.opcua.stack.core.types.structured.WriteRequest$$Lambda$441/572212830.encode(Unknown Source)
at com.digitalpetri.opcua.stack.core.serialization.binary.BinaryEncoder.encodeMessage(BinaryEncoder.java:642)
at com.digitalpetri.opcua.stack.client.handlers.UaTcpClientSymmetricHandler.lambda$encode$25(UaTcpClientSymmetricHandler.java:101)
at com.digitalpetri.opcua.stack.client.handlers.UaTcpClientSymmetricHandler$$Lambda$572/942024036.accept(Unknown Source)
at com.digitalpetri.opcua.stack.core.channel.SerializationQueue.lambda$encode$1(SerializationQueue.java:57)
at com.digitalpetri.opcua.stack.core.channel.SerializationQueue$$Lambda$555/1742350697.run(Unknown Source)
at com.digitalpetri.opcua.stack.core.util.ExecutionQueue$PollAndExecute.run(ExecutionQueue.java:110)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)`

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<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [February 1, 2016, 1:17pm UTC](https://forum.inductiveautomation.com/t/executionqueue-uncaught-throwable-during-execution/11150/2 "2016-02-01T13:17:55Z")

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I think this was either fixed, or the error handling improved so the write fails earlier and explains what datatype it doesn’t know about, for 7.8.1. Can you upgrade and try it again?