diff --git a/mpbackup b/mpbackup
index b3369f3..e6ac7a4 100644
--- a/mpbackup
+++ b/mpbackup
@@ -18,6 +18,11 @@ def unset_restic_vars
   ENV.delete('RESTIC_PASSWORD')
 end
 
+def error(exit_status, message)
+  STDERR.puts("Error: #{message}")
+  exit exit_status
+end
+
 unset_restic_vars
 
 options = {}
@@ -50,8 +55,7 @@ else
 end
 
 if !Pathname.new(config_file).exist? then
-  STDERR.puts "Config file #{config_file} has not been found!"
-  exit 1
+  error(1, "Config file #{config_file} has not been found!")
 end
 
 def do_backup(config)
@@ -74,8 +78,7 @@ def do_backup(config)
   puts("Command: #{backup_command.join(' ')}")
   system(*backup_command)
   if $?.exitstatus > 0
-    STDERR.puts 'Failed to do backup.'
-    exit 1
+    error(1, 'Failed to do backup.')
   end
 
   puts 'Checking restic repo …'
@@ -83,8 +86,7 @@ def do_backup(config)
   puts("Command: #{check_command.join(' ')}")
   system(*check_command)
   if $?.exitstatus > 0
-    STDERR.puts "Checking restic repository #{ENV['RESTIC_REPOSITORY']} failed."
-    exit 1
+    error(1, "Checking restic repository #{ENV['RESTIC_REPOSITORY']} failed.")
   end
 
   if config.dig('forget', 'enable')
@@ -97,8 +99,7 @@ def do_backup(config)
     # Data will only be deleted when `restic prune` is executed or when
     # `restic forget` is called with `--prune`.
     if $?.exitstatus > 0
-      STDERR.puts "Forgetting snapshots failed."
-      exit 1
+      error(1, "Forgetting snapshots failed.")
     end
   end
 
@@ -113,11 +114,13 @@ if config_names.empty?
     "configuration from the file (‘#{configs.dig(0, 'name')}’)."
   do_backup(configs[0])
 else
-  config_names.each do |config_name|
-    configs.each do |config|
-      if config_name == config['name']
-        do_backup(config)
-      end
+  config_hash = configs.map {|c| [c['name'], c]}.to_h
+  config_names.each do |name|
+    if !config_hash.key? name
+      error(1, "Cannot find configuration ‘#{name}’.")
     end
   end
+  config_names.each do |config_name|
+    do_backup(config_hash[config_name])
+  end
 end