diff --git a/apps/el-gen/envsubst.py b/apps/el-gen/envsubst.py
new file mode 100644
index 0000000..8874ee4
--- /dev/null
+++ b/apps/el-gen/envsubst.py
@@ -0,0 +1,23 @@
+import os
+import re
+import sys
+
+from dotenv import dotenv_values
+
+config = dotenv_values(os.environ['FULL_ENV_FILE'])
+
+bracket_sub_re = re.compile(r'\${(\w+)}')
+basic_sub_re = re.compile(r'\$([A-Z0-9_]+)')
+
+
+def sub(m):
+    cfg = config.get(m.group(1), None)
+    if cfg is None:
+        raise Exception(f"Missing environment variable {m.group(1)}")
+    return cfg
+
+
+for line in sys.stdin:
+    out = bracket_sub_re.sub(sub, line)
+    out = basic_sub_re.sub(sub, out)
+    sys.stdout.write(out)
diff --git a/apps/el-gen/requirements.txt b/apps/el-gen/requirements.txt
index 78fabe0..68cb490 100644
--- a/apps/el-gen/requirements.txt
+++ b/apps/el-gen/requirements.txt
@@ -1,3 +1,4 @@
 ruamel.yaml==0.17.16
 web3>=6.15.0
-setuptools>=69.1.0
\ No newline at end of file
+setuptools>=69.1.0
+python-dotenv==1.0.1
\ No newline at end of file
diff --git a/entrypoint.sh b/entrypoint.sh
index 4f51af0..30cb661 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -1,9 +1,15 @@
 #!/bin/bash -e
+export FULL_ENV_FILE="/defaults/defaults.env"
+
 if [ -f /config/values.env ];
 then
-    source /config/values.env
+    export FULL_ENV_FILE="/config/values.env"
 fi
-source /defaults/defaults.env
+
+# Pull these values out of the env file since they can be very large and cause
+# "arguments list too long" errors in the shell.
+grep -v "ADDITIONAL_PRELOADED_CONTRACTS" $FULL_ENV_FILE | grep -v "EL_PREMINE_ADDRS" > /tmp/values-short.env
+source /tmp/values-short.env
 
 SERVER_ENABLED="${SERVER_ENABLED:-false}"
 SERVER_PORT="${SERVER_PORT:-8000}"
@@ -30,7 +36,7 @@ gen_el_config(){
     if ! [ -f "/data/metadata/genesis.json" ]; then
         tmp_dir=$(mktemp -d -t ci-XXXXXXXXXX)
         mkdir -p /data/metadata
-        envsubst < /config/el/genesis-config.yaml > $tmp_dir/genesis-config.yaml
+        python3 /apps/el-gen/envsubst.py < /config/el/genesis-config.yaml > $tmp_dir/genesis-config.yaml
         python3 /apps/el-gen/genesis_geth.py $tmp_dir/genesis-config.yaml      > /data/metadata/genesis.json
         python3 /apps/el-gen/genesis_chainspec.py $tmp_dir/genesis-config.yaml > /data/metadata/chainspec.json
         python3 /apps/el-gen/genesis_besu.py $tmp_dir/genesis-config.yaml > /data/metadata/besu.json