diff --git a/install_check.pl b/install_check.pl
index 03b3aa1..6c1bff7 100644
--- a/install_check.pl
+++ b/install_check.pl
@@ -1,5 +1,8 @@
 # install_check.pl
+use strict;
+use warnings;
 
+our %config;
 do 'jailkit-lib.pl';
 
 # is_installed(mode)
diff --git a/jailkit-lib.pl b/jailkit-lib.pl
index 99c7593..82de1eb 100644
--- a/jailkit-lib.pl
+++ b/jailkit-lib.pl
@@ -1,5 +1,4 @@
 #!/usr/bin/perl
-
 use strict;
 use warnings;
 
diff --git a/t/all_ok.t b/t/all_ok.t
new file mode 100644
index 0000000..1dcc3df
--- /dev/null
+++ b/t/all_ok.t
@@ -0,0 +1,6 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+use Test::Strict 'no_plan';
+
+all_perl_files_ok();