diff --git a/docker/substitute-env-variables.sh b/docker/substitute-env-variables.sh
index 73be4a6..bd3d9cb 100755
--- a/docker/substitute-env-variables.sh
+++ b/docker/substitute-env-variables.sh
@@ -1,5 +1,7 @@
 #!/bin/bash
 
+echo 'Substituting environment variables...'
+
 # The first parameter is a comma-delimited list of paths to files which should be substituted
 if [[ -z $1 ]]; then
   echo 'ERROR: No target files given.'
@@ -7,16 +9,17 @@ if [[ -z $1 ]]; then
 fi
 
 env_list='\$PRODUCTION \$API_URL \$IRB_URL \$HOME_ROUTE \$PORT0'
-for i in $(echo $1 | sed "s/,/ /g")
+for file_path in $(echo $1 | sed "s/,/ /g")
 do
-  # Replace strings in the given file(s) in env_list
-  envsubst "$env_list" < "$i" > "$i".tmp && mv "$i".tmp "$i"
+  echo "replacing $env_list in $file_path"
 
-  # Set DEBUG=true in order to log the replaced file
-  if [ "$DEBUG" = true ] ; then
-    exec cat $i
-  fi
+  # Replace strings in the given file(s) in env_list
+  envsubst "$env_list" < "$file_path" > "$file_path".tmp && mv "$file_path".tmp "$file_path"
+
+  echo '...'
 done
 
+echo 'Finished substituting environment variables.'
+
 # Execute all other commands with parameters
 exec "${@:2}"