diff --git a/CHANGES.rst b/CHANGES.rst
index f6636a8d..e9ea4c0a 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,7 +4,9 @@
 Bug Fixes
 ---------
 
--
+- Adding "IMAGER" as another allowed value for the "MRSPRCHN"
+  keyword, in order to support proper handling of MIRI MRS
+  and Imager exposures done in parallel. [#259]
 
 Changes to API
 --------------
diff --git a/src/stdatamodels/jwst/datamodels/schemas/core.schema.yaml b/src/stdatamodels/jwst/datamodels/schemas/core.schema.yaml
index c5ddde4c..853b9a42 100644
--- a/src/stdatamodels/jwst/datamodels/schemas/core.schema.yaml
+++ b/src/stdatamodels/jwst/datamodels/schemas/core.schema.yaml
@@ -1332,7 +1332,7 @@ properties:
           primary_channel:
             title: MRS primary channel
             type: string
-            enum: [ALL, CHANNEL1, CHANNEL2, CHANNEL3, CHANNEL4]
+            enum: [ALL, CHANNEL1, CHANNEL2, CHANNEL3, CHANNEL4, IMAGER]
             fits_keyword: MRSPRCHN
           dithered_ra:
             title: RA of dithered pointing location