diff --git a/app/data/container-build/cerc-fixturenet-eth-geth/Dockerfile b/app/data/container-build/cerc-fixturenet-eth-geth/Dockerfile
index 666f9117..dc81eb06 100644
--- a/app/data/container-build/cerc-fixturenet-eth-geth/Dockerfile
+++ b/app/data/container-build/cerc-fixturenet-eth-geth/Dockerfile
@@ -22,6 +22,18 @@ COPY run-el.sh /opt/testnet/run.sh
 RUN cd /opt/testnet && make genesis-el
 
 COPY --from=geth  /usr/local/bin/geth /usr/local/bin/
+
+# Snag the genesis block info.
 RUN geth --datadir ~/ethdata init /opt/testnet/build/el/geth.json && rm -f ~/ethdata/geth/nodekey
+RUN cp -rp ~/ethdata ~/tmpeth && \
+    geth --datadir ~/tmpeth init /opt/testnet/build/el/geth.json && \
+    geth --datadir ~/tmpeth --http & \
+    sleep 5 && \
+    curl -q --location 'localhost:8545' \
+        --header 'Content-Type: application/json' \
+        --data '{ "jsonrpc": "2.0", "id": 14, "method": "eth_getBlockByNumber", "params": ["0x0", false] }' \
+        -o /opt/testnet/build/el/genesis_block.json && \
+    killall -9 geth && \
+    rm -rf ~/tmpeth
 
 ENTRYPOINT ["/opt/testnet/run.sh"]
diff --git a/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/build_cl.sh b/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/build_cl.sh
index 2245fe0e..50b3e4e6 100755
--- a/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/build_cl.sh
+++ b/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/build_cl.sh
@@ -34,6 +34,7 @@ lcli \
   --altair-fork-epoch $ALTAIR_FORK_EPOCH \
   --bellatrix-fork-epoch $MERGE_FORK_EPOCH \
   --eth1-id $ETH1_CHAIN_ID \
+  --eth1-block-hash $ETH1_BLOCK_HASH \
   --eth1-follow-distance 1 \
   --seconds-per-slot $SECONDS_PER_SLOT \
   --seconds-per-eth1-block $SECONDS_PER_ETH1_BLOCK \
diff --git a/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/vars.env b/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/vars.env
index b8c27349..f2060a9a 100644
--- a/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/vars.env
+++ b/app/data/container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/vars.env
@@ -42,7 +42,9 @@ VC_ARGS=${VC_ARGS:-""}
 EXECUTION_ENDPOINT=${EXECUTION_ENDPOINT:-http://localhost:8551}
 
 ETH1_GENESIS_JSON=${ETH1_GENESIS_JSON:-"../build/el/geth.json"}
+ETH1_GENESIS_BLOCK_JSON=${ETH1_GENESIS_BLOCK_JSON:-"../build/el/genesis_block.json"}
 ETH1_CONFIG_YAML=${ETH1_CONFIG_YAML:-"../el/el-config.yaml"}
+ETH1_BLOCK_HASH=${ETH1_BLOCK_HASH:-`cat $ETH1_GENESIS_BLOCK_JSON | jq -r '.result.hash' | cut -d'x' -f2`}
 
 ETH1_CHAIN_ID=${ETH1_CHAIN_ID:-`cat $ETH1_GENESIS_JSON | jq -r '.config.chainId'`}
 ETH1_TTD=${ETH1_TTD:-`cat $ETH1_GENESIS_JSON | jq -r '.config.terminalTotalDifficulty'`}