diff --git a/util/prepare.sh b/util/prepare.sh
index 46859354..6041c5d1 100755
--- a/util/prepare.sh
+++ b/util/prepare.sh
@@ -1,6 +1,15 @@
 #!/bin/bash
 
 source .env
-envsubst < chains/chains_mainnet.json > chains/chains_mainnet.json
-envsubst < chains/chains_testnet.json > chains/chains_testnet.json
+
+originalfile="chains/chains_mainnet.json"
+tmpfile=$(mktemp)
+cp --attributes-only --preserve $originalfile $tmpfile
+cat $originalfile | envsubst > $tmpfile && mv $tmpfile $originalfile
+
+originalfile="chains/chains_testnet.json"
+tmpfile=$(mktemp)
+cp --attributes-only --preserve $originalfile $tmpfile
+cat $originalfile | envsubst > $tmpfile && mv $tmpfile $originalfile
+
 chown -R 1005:1001 chains bootstrap_skript
\ No newline at end of file