diff --git a/CHANGES.rst b/CHANGES.rst
index 9bc5afb17..0ca02bf50 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,10 @@
+11.17.6 (2023-09-08)
+=====================
+
+JWST
+----
+
+- Added a substitution to miri_ipc [#958]
 
 11.17.5 (2023-09-07)
 =====================
diff --git a/crds/jwst/specs/combined_specs.json b/crds/jwst/specs/combined_specs.json
index 24d6a2c93..1784fffc0 100644
--- a/crds/jwst/specs/combined_specs.json
+++ b/crds/jwst/specs/combined_specs.json
@@ -1237,10 +1237,20 @@
             "observatory":"JWST",
             "parkey":[
                 [
-                    "META.INSTRUMENT.DETECTOR"
+                    "META.INSTRUMENT.DETECTOR",
+                    "META.SUBARRAY.NAME"
+                ],
+                [
+                    "META.OBSERVATION.DATE",
+                    "META.OBSERVATION.TIME"
                 ]
             ],
-            "sha1sum":"02e9c784a6c48a9c1a6952fb68a9b0d35fc2f28e",
+            "sha1sum":"8c4873a3341cc3132d29b8b447535db189c6d826",
+            "substitutions":{
+                "META.DETECTOR":{
+                    "GENERIC":"N/A"
+                }
+            },
             "suffix":"ipc",
             "text_descr":"Interpixel Capacitance",
             "tpn":"miri_ipc.tpn",
diff --git a/crds/jwst/specs/miri_ipc.rmap b/crds/jwst/specs/miri_ipc.rmap
index 448a411ae..15912db16 100644
--- a/crds/jwst/specs/miri_ipc.rmap
+++ b/crds/jwst/specs/miri_ipc.rmap
@@ -7,8 +7,13 @@ header = {
     'mapping' : 'REFERENCE',
     'name' : 'miri_ipc.rmap',
     'observatory' : 'JWST',
-    'parkey' : (('META.INSTRUMENT.DETECTOR',),),
-    'sha1sum' : '02e9c784a6c48a9c1a6952fb68a9b0d35fc2f28e',
+    'parkey' : (('META.INSTRUMENT.DETECTOR', 'META.SUBARRAY.NAME'), ('META.OBSERVATION.DATE', 'META.OBSERVATION.TIME')),
+    'sha1sum' : '8c4873a3341cc3132d29b8b447535db189c6d826',
+    'substitutions' : {
+        'META.DETECTOR' : {
+            'GENERIC' : 'N/A',
+        },
+    },
     'suffix' : 'ipc',
     'text_descr' : 'Interpixel Capacitance',
 }