diff --git a/beacon-chain/p2p/discovery.go b/beacon-chain/p2p/discovery.go
index a8b0f59d6bb3..eeb03c8f15ec 100644
--- a/beacon-chain/p2p/discovery.go
+++ b/beacon-chain/p2p/discovery.go
@@ -181,9 +181,16 @@ func (s *Service) RefreshPersistentSubnets() {
 
 	// Get the current attestation subnet bitfield.
 	bitV := bitfield.NewBitvector64()
-	attestationCommittees := cache.SubnetIDs.GetAllSubnets()
-	for _, idx := range attestationCommittees {
-		bitV.SetBitAt(idx, true)
+	if flags.Get().SubscribeToAllSubnets {
+		// Set all 64 bits for all attestation subnets
+		for i := uint64(0); i < params.BeaconConfig().AttestationSubnetCount; i++ {
+			bitV.SetBitAt(i, true)
+		}
+	} else {
+		attestationCommittees := cache.SubnetIDs.GetAllSubnets()
+		for _, idx := range attestationCommittees {
+			bitV.SetBitAt(idx, true)
+		}
 	}
 
 	// Get the attestation subnet bitfield we store in our record.
diff --git a/changelog/samcm_fix-attnets-metadata-all-subnets.md b/changelog/samcm_fix-attnets-metadata-all-subnets.md
new file mode 100644
index 000000000000..e903d59ac76b
--- /dev/null
+++ b/changelog/samcm_fix-attnets-metadata-all-subnets.md
@@ -0,0 +1,3 @@
+### Fixed
+
+- Fixed `--subscribe-all-subnets` flag to correctly advertise all 64 attestation subnets in reqresp metadata.