# Annotations after set\_bipolar\_reference

**URL:** <https://mne.discourse.group/t/annotations-after-set-bipolar-reference/5272>\
**Category:** Support & Discussions\
**Created:** [July 15, 2022, 11:18am UTC](https://mne.discourse.group/t/annotations-after-set-bipolar-reference/5272 "2022-07-15T11:18:45Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mnaomi](https://avatars.discourse-cdn.com/v4/letter/m/8797f3/32.png) [@mnaomi](https://mne.discourse.group/u/mnaomi)\
**Post date:** [July 15, 2022, 11:18am UTC](https://mne.discourse.group/t/annotations-after-set-bipolar-reference/5272/1 "2022-07-15T11:18:45Z")

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Hi, I’ve succesfully used mne.Annotations to annotate EEG data for a while now. However, today I created a bipolar montage (instead of the reference channels I used before) using set\_bipolar\_reference and when I now run the code, it gives the following error:

ValueError: At least one channel name in annotations missing from info: FP1-REF-F7-REF

Does anyone know how I can fix this?

- MNE version: e.g. 0.24.0
- operating system: Windows 10

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**Author:** ![mscheltienne](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/mscheltienne/32/827_2.png) [@mscheltienne](https://mne.discourse.group/u/mscheltienne)\
**Post date:** [July 15, 2022, 11:49am UTC](https://mne.discourse.group/t/annotations-after-set-bipolar-reference/5272/2 "2022-07-15T11:49:58Z")

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Hello,

What code is throwing this error?  
Note that `set_bipolar_reference` adds a new virtual channel and drops the channels used to build this virtual channel. If you want to retain the channels used to build the virtual channel, you should provide the argument `drop_refs=False`. c.f. the API page: [mne.set\_bipolar\_reference — MNE 1.0.3 documentation](https://mne.tools/stable/generated/mne.set_bipolar_reference.html)

Mathieu