diff --git a/configs/mainnet/altair.yaml b/configs/mainnet/altair.yaml
index 2e4839c16..d7daf6028 100644
--- a/configs/mainnet/altair.yaml
+++ b/configs/mainnet/altair.yaml
@@ -33,7 +33,18 @@ EPOCHS_PER_SYNC_COMMITTEE_PERIOD: 256
 DOMAIN_SYNC_COMMITTEE: 0x07000000
 
 
+# Fork
+# ---------------------------------------------------------------
+ALTAIR_FORK_VERSION: 0x01000000
+# TBD
+ALTAIR_FORK_SLOT: 0
+
+
 # Sync protocol
 # ---------------------------------------------------------------
+# 1
+MIN_SYNC_COMMITTEE_PARTICIPANTS: 1
+# 2**13
+MAX_VALID_LIGHT_CLIENT_UPDATES: 8192
 # 2**13 (=8192)
 LIGHT_CLIENT_UPDATE_TIMEOUT: 8192
diff --git a/configs/minimal/altair.yaml b/configs/minimal/altair.yaml
index 80233404d..dc0491d60 100644
--- a/configs/minimal/altair.yaml
+++ b/configs/minimal/altair.yaml
@@ -33,7 +33,18 @@ EPOCHS_PER_SYNC_COMMITTEE_PERIOD: 8
 DOMAIN_SYNC_COMMITTEE: 0x07000000
 
 
+# Fork
+# ---------------------------------------------------------------
+ALTAIR_FORK_VERSION: 0x01000000
+# [customized]
+ALTAIR_FORK_SLOT: 0
+
+
 # Sync protocol
 # ---------------------------------------------------------------
+# 1
+MIN_SYNC_COMMITTEE_PARTICIPANTS: 1
+# [customized]
+MAX_VALID_LIGHT_CLIENT_UPDATES: 32
 # [customized]
 LIGHT_CLIENT_UPDATE_TIMEOUT: 32