diff --git a/letsencrypt-nginx/letsencrypt_nginx/configurator.py b/letsencrypt-nginx/letsencrypt_nginx/configurator.py
index f759dc7c1..2899e1f76 100644
--- a/letsencrypt-nginx/letsencrypt_nginx/configurator.py
+++ b/letsencrypt-nginx/letsencrypt_nginx/configurator.py
@@ -444,7 +444,7 @@ class NginxConfigurator(common.Plugin):
         # nginx < 0.8.48 uses machine hostname as default server_name instead of
         # the empty string
         if nginx_version < (0, 8, 48):
-            raise errors.PluginError("Nginx version must be 0.8.48+")
+            raise errors.NotSupportedError("Nginx version must be 0.8.48+")
 
         return nginx_version
 
diff --git a/letsencrypt-nginx/letsencrypt_nginx/tests/configurator_test.py b/letsencrypt-nginx/letsencrypt_nginx/tests/configurator_test.py
index d8f82bd05..3703a8201 100644
--- a/letsencrypt-nginx/letsencrypt_nginx/tests/configurator_test.py
+++ b/letsencrypt-nginx/letsencrypt_nginx/tests/configurator_test.py
@@ -249,7 +249,7 @@ class NginxConfiguratorTest(util.NginxTest):
                            " (based on LLVM 3.5svn)",
                            "TLS SNI support enabled",
                            "configure arguments: --with-http_ssl_module"]))
-        self.assertRaises(errors.PluginError, self.config.get_version)
+        self.assertRaises(errors.NotSupportedError, self.config.get_version)
 
         mock_popen.side_effect = OSError("Can't find program")
         self.assertRaises(errors.PluginError, self.config.get_version)
diff --git a/letsencrypt/interfaces.py b/letsencrypt/interfaces.py
index b07e64894..3a0732b64 100644
--- a/letsencrypt/interfaces.py
+++ b/letsencrypt/interfaces.py
@@ -102,14 +102,19 @@ class IPlugin(zope.interface.Interface):
     def prepare():
         """Prepare the plugin.
 
-         Finish up any additional initialization.
+        Finish up any additional initialization.
 
-         :raises .MisconfigurationError:
-             when full initialization cannot be completed. Plugin will
-             be displayed on a list of available plugins.
-         :raises .NoInstallationError:
-             when the necessary programs/files cannot be located. Plugin
-             will NOT be displayed on a list of available plugins.
+        :raises .PluginError:
+            when full initialization cannot be completed.
+        :raises .MisconfigurationError:
+            when full initialization cannot be completed. Plugin will
+            be displayed on a list of available plugins.
+        :raises .NoInstallationError:
+            when the necessary programs/files cannot be located. Plugin
+            will NOT be displayed on a list of available plugins.
+        :raises .NotSupportedError:
+            when the installation is recognized, but the version is not
+            currently supported.
 
         """