# Error when running watershed

**URL:** <https://discourse.slicer.org/t/error-when-running-watershed/48557>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [October 21, 2026, 2:38pm UTC](https://discourse.slicer.org/t/error-when-running-watershed/48557 "2026-10-21T14:38:57Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![jsguerra](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@jsguerra](https://discourse.slicer.org/u/jsguerra)\
**Post date:** [October 21, 2026, 2:38pm UTC](https://discourse.slicer.org/t/error-when-running-watershed/48557/1 "2026-10-21T14:38:57Z")

</div>

I’m trying to use watershed segmentation (5.12.4 on Win10) and I get a segmentation fail message. This is what I get on detials:

> Traceback (most recent call last):
> 
> File “C:\Users/JSG/AppData/Local/slicer.org/3D Slicer 5.12.4/bin/Python\slicer\util.py”, line 3614, in tryWithErrorDisplay
> 
> ```
> yield
> 
> ```
> 
> File “C:\Users\JSG\AppData\Local\slicer.org\3D Slicer 5.12.4\lib\Slicer-5.12\qt-scripted-modules\SegmentEditorEffects\AbstractScriptedSegmentEditorAutoCompleteEffect.py”, line 303, in onPreview
> 
> ```
> self.preview()
> 
> ```
> 
> File “C:\Users\JSG\AppData\Local\slicer.org\3D Slicer 5.12.4\lib\Slicer-5.12\qt-scripted-modules\SegmentEditorEffects\AbstractScriptedSegmentEditorAutoCompleteEffect.py”, line 567, in preview
> 
> ```
> self.computePreviewLabelmap(mergedImage, outputLabelmap)
> 
> ```
> 
> File “C:/Users/JSG/AppData/Local/slicer.org/3D Slicer 5.12.4/slicer.org/Extensions-34645/SegmentEditorExtraEffects/lib/Slicer-5.12/qt-scripted-modules/SegmentEditorWatershedLib/SegmentEditorEffect.py”, line 111, in computePreviewLabelmap
> 
> ```
> labelImage = sitk.ReadImage(sitkUtils.GetSlicerITKReadWriteAddress(mergedLabelmapNode.GetName()))
> 
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> ```
> 
> File “C:\Users\JSG\AppData\Local\slicer.org\3D Slicer 5.12.4\lib\Python\Lib\site-packages\SimpleITK\extra.py”, line 384, in ReadImage
> 
> ```
> return reader.Execute()
> 
> ^^^^^^^^^^^^^^^^
> 
> ```
> 
> File “C:\Users\JSG\AppData\Local\slicer.org\3D Slicer 5.12.4\lib\Python\Lib\site-packages\SimpleITK\SimpleITK.py”, line 8534, in Execute
> 
> ```
> return \_SimpleITK.ImageFileReader_Execute(self)
> 
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> ```
> 
> RuntimeError: Exception thrown in SimpleITK ImageFileReader\_Execute: D:\a\SimpleITK\SimpleITK\Code\IO\src\sitkImageReaderBase.cxx:91:
> 
> sitk::ERROR: The file “slicer:0000023F71755F30#vtkMRMLLabelMapVolumeNode1” does not exist.

I created two segments and placed seeds in them. I am doing something wrong?