diff --git a/configs/mainnet.yaml b/configs/mainnet.yaml
index 99bba1d4e..078b2cced 100644
--- a/configs/mainnet.yaml
+++ b/configs/mainnet.yaml
@@ -146,3 +146,8 @@ DOMAIN_SHARD_PROPOSAL: 0x80000000
 DOMAIN_SHARD_COMMITTEE: 0x81000000
 DOMAIN_LIGHT_CLIENT: 0x82000000
 DOMAIN_CUSTODY_BIT_SLASHING: 0x83000000
+
+
+# Phase 1
+# ---------------------------------------------------------------
+INITIAL_ACTIVE_SHARDS: 64
diff --git a/configs/minimal.yaml b/configs/minimal.yaml
index 4aacf17e1..90af6605f 100644
--- a/configs/minimal.yaml
+++ b/configs/minimal.yaml
@@ -153,9 +153,5 @@ DOMAIN_CUSTODY_BIT_SLASHING: 0x83000000
 
 # Phase 1
 # ---------------------------------------------------------------
-SHARD_SLOTS_PER_BEACON_SLOT: 2
-EPOCHS_PER_SHARD_PERIOD: 4
-# PHASE_1_FORK_EPOCH >= EPOCHS_PER_SHARD_PERIOD * 2
-PHASE_1_FORK_EPOCH: 8
-# PHASE_1_FORK_SLOT = PHASE_1_FORK_EPOCH * SLOTS_PER_EPOCH
-PHASE_1_FORK_SLOT: 64
+# [customized] reduced for testing
+INITIAL_ACTIVE_SHARDS: 4