diff --git a/tools/gen_auth_tokens.sh b/tools/gen_auth_tokens.sh
index 344a92e3..4fdbaa79 100755
--- a/tools/gen_auth_tokens.sh
+++ b/tools/gen_auth_tokens.sh
@@ -27,16 +27,14 @@ generate_token() {
 }
 
 write_token() {
-  local auth_level="$1" $(echo "$1" | tr '[:lower:]' '[:upper:]')
+  local auth_level="$1"
   local token="$2"
 
   local auth_level=$(echo "$auth_level" | tr '[:lower:]' '[:upper:]')
 
   local var_name="CELESTIA_NODE_AUTH_TOKEN_${auth_level}"
 
-  sed -i '.bak' -e "s/.*$var_name.*/$var_name=$token/" "$DOTENV"
-  rm "$DOTENV.bak" # there's no compatible way to tell sed not to do a backup file
-                   # accept it and remove the file afterwards
+  ex "+%s/.*$var_name.*/$var_name=$token/" -scwq "$DOTENV"
 }
 
 main() {