diff --git a/specs/electra/validator.md b/specs/electra/validator.md
index 2e980d5345..3620c30790 100644
--- a/specs/electra/validator.md
+++ b/specs/electra/validator.md
@@ -24,6 +24,8 @@
     - [Deposits](#deposits)
     - [Execution payload](#execution-payload)
     - [Execution Requests](#execution-requests)
+  - [Constructing the `BlobSidecar`s](#constructing-the-blobsidecars)
+    - [Sidecar](#sidecar)
 - [Attesting](#attesting)
   - [Construct attestation](#construct-attestation)
 - [Attestation aggregation](#attestation-aggregation)
@@ -240,6 +242,17 @@ def get_execution_requests(execution_requests_list: Sequence[bytes]) -> Executio
     )
 ```
 
+### Constructing the `BlobSidecar`s
+
+#### Sidecar
+
+*[Modified in Electra:EIP7691]*
+
+```python
+def compute_subnet_for_blob_sidecar(blob_index: BlobIndex) -> SubnetID:
+    return SubnetID(blob_index % BLOB_SIDECAR_SUBNET_COUNT_ELECTRA)
+```
+
 ## Attesting
 
 ### Construct attestation