diff --git a/MANIFEST b/MANIFEST
index c57481d..2b2c5fa 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -54,6 +54,7 @@ README.md
 SECURITY.md
 t/lib/Test/ACME2_Server.pm
 t/lib/Test/Crypt.pm
+t/Net-ACME2-api-guards.t
 t/Net-ACME2-AccountKey.t
 t/Net-ACME2-Authorization.t
 t/Net-ACME2-Challenge-dns_01.t
diff --git a/lib/Net/ACME2.pm b/lib/Net/ACME2.pm
index 3fccf94..64a054b 100644
--- a/lib/Net/ACME2.pm
+++ b/lib/Net/ACME2.pm
@@ -1144,8 +1144,6 @@ sub _set_http {
     return;
 }
 
-our $_POST_METHOD;
-
 sub _post {
     my ( $self, $link_name, $data ) = @_;
 
diff --git a/t/Net-ACME2-api-guards.t b/t/Net-ACME2-api-guards.t
new file mode 100644
index 0000000..e10ae59
--- /dev/null
+++ b/t/Net-ACME2-api-guards.t
@@ -0,0 +1,115 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+use Test::More;
+use Test::Exception;
+use Test::FailWarnings;
+
+use FindBin;
+use lib "$FindBin::Bin/lib";
+use Test::ACME2_Server;
+
+#----------------------------------------------------------------------
+
+{
+    package MyCA;
+
+    use parent qw( Net::ACME2 );
+
+    use constant {
+        HOST => 'acme.someca.net',
+        DIRECTORY_PATH => '/acme-directory',
+    };
+}
+
+my $_P256_KEY = <<END;
+-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIKDv8TBijBVbTYB7lfUnwLn4qjqWD0GD7XOXzdp0wb61oAoGCCqGSM49
+AwEHoUQDQgAEBJIULcFadtIBc0TuNzT80UFcfkQ0U7+EPqEJNXamG1H4/z8xVgE7
+3hoBfX4xbN2Hx2p26eNIptt+1jj2H/M44g==
+-----END EC PRIVATE KEY-----
+END
+
+#----------------------------------------------------------------------
+# new() requires key
+
+subtest 'new() without key throws' => sub {
+    my $SERVER_OBJ = Test::ACME2_Server->new(
+        ca_class => 'MyCA',
+    );
+
+    throws_ok(
+        sub { MyCA->new() },
+        qr/key/i,
+        'new() dies without key',
+    );
+};
+
+#----------------------------------------------------------------------
+# http_timeout() - sync mode passthrough
+
+subtest 'http_timeout() in sync mode' => sub {
+    my $SERVER_OBJ = Test::ACME2_Server->new(
+        ca_class => 'MyCA',
+    );
+
+    my $acme = MyCA->new( key => $_P256_KEY );
+
+    my $timeout = $acme->http_timeout();
+    ok( defined $timeout, 'http_timeout() returns a value in sync mode' );
+
+    lives_ok(
+        sub { $acme->http_timeout(30) },
+        'http_timeout() accepts a new value',
+    );
+
+    is( $acme->http_timeout(), 30, 'http_timeout() reflects the new value' );
+};
+
+#----------------------------------------------------------------------
+# http_timeout() - async mode dies
+
+subtest 'http_timeout() in async mode dies' => sub {
+    my $SERVER_OBJ = Test::ACME2_Server->new(
+        ca_class => 'MyCA',
+    );
+
+    {
+        package MockAsyncUA;
+
+        sub new { bless {}, shift }
+        sub request { die "should not be called" }
+    }
+
+    my $acme = MyCA->new(
+        key => $_P256_KEY,
+        async_ua => MockAsyncUA->new(),
+    );
+
+    throws_ok(
+        sub { $acme->http_timeout() },
+        qr/asynchronous mode/,
+        'http_timeout() dies in async mode',
+    );
+};
+
+#----------------------------------------------------------------------
+# update_account() without key_id
+
+subtest 'update_account() without key_id throws' => sub {
+    my $SERVER_OBJ = Test::ACME2_Server->new(
+        ca_class => 'MyCA',
+    );
+
+    my $acme = MyCA->new( key => $_P256_KEY );
+
+    throws_ok(
+        sub { $acme->update_account( contact => ['mailto:test@example.com'] ) },
+        qr/key ID/i,
+        'update_account() dies without key_id',
+    );
+};
+
+done_testing();