diff --git a/letsencrypt-apache/letsencrypt_apache/configurator.py b/letsencrypt-apache/letsencrypt_apache/configurator.py
index 98b0b8820..ba3bdcd7d 100644
--- a/letsencrypt-apache/letsencrypt_apache/configurator.py
+++ b/letsencrypt-apache/letsencrypt_apache/configurator.py
@@ -86,17 +86,17 @@ class ApacheConfigurator(augeas_configurator.AugeasConfigurator):
 
     @classmethod
     def add_parser_arguments(cls, add):
-        add("ctl", default=constants.CLI_DEFAULTS["ctl"],
+        add("ctl", default=constants.os_constant("ctl"),
             help="Path to the 'apache2ctl' binary, used for 'configtest', "
                  "retrieving the Apache2 version number, and initialization "
                  "parameters.")
-        add("enmod", default=constants.CLI_DEFAULTS["enmod"],
+        add("enmod", default=constants.os_constant("enmod"),
             help="Path to the Apache 'a2enmod' binary.")
-        add("dismod", default=constants.CLI_DEFAULTS["dismod"],
+        add("dismod", default=constants.os_constant("dismod"),
             help="Path to the Apache 'a2enmod' binary.")
-        add("le-vhost-ext", default=constants.CLI_DEFAULTS["le_vhost_ext"],
+        add("le-vhost-ext", default=constants.os_constant("le_vhost_ext"),
             help="SSL vhost configuration extension.")
-        add("server-root", default=constants.CLI_DEFAULTS["server_root"],
+        add("server-root", default=constants.os_constant("server_root"),
             help="Apache server root directory.")
         le_util.add_deprecated_argument(add, "init-script", 1)
 
@@ -583,7 +583,7 @@ class ApacheConfigurator(augeas_configurator.AugeasConfigurator):
 
         Duplicates vhost and adds default ssl options
         New vhost will reside as (nonssl_vhost.path) +
-        ``letsencrypt_apache.constants.CLI_DEFAULTS["le_vhost_ext"]``
+        ``letsencrypt_apache.constants.os_constant("le_vhost_ext")``
 
         .. note:: This function saves the configuration
 
diff --git a/letsencrypt-apache/letsencrypt_apache/constants.py b/letsencrypt-apache/letsencrypt_apache/constants.py
index 202fc3e21..e302a29fe 100644
--- a/letsencrypt-apache/letsencrypt_apache/constants.py
+++ b/letsencrypt-apache/letsencrypt_apache/constants.py
@@ -1,14 +1,27 @@
 """Apache plugin constants."""
 import pkg_resources
+from letsencrypt import le_util
 
 
-CLI_DEFAULTS = dict(
+CLI_DEFAULTS_DEBIAN = dict(
     server_root="/etc/apache2",
     ctl="apache2ctl",
     enmod="a2enmod",
     dismod="a2dismod",
     le_vhost_ext="-le-ssl.conf",
 )
+CLI_DEFAULTS_CENTOS = dict(
+    server_root="/etc/httpd",
+    ctl="apachectl",
+    enmod=None,
+    dismod=None,
+    le_vhost_ext="-le-ssl.conf",
+)
+CLI_DEFAULTS = {
+    "debian": CLI_DEFAULTS_DEBIAN,
+    "ubuntu": CLI_DEFAULTS_DEBIAN,
+    "centos": CLI_DEFAULTS_CENTOS
+}
 """CLI defaults."""
 
 MOD_SSL_CONF_DEST = "options-ssl-apache.conf"
@@ -38,3 +51,10 @@ UIR_ARGS = ["always", "set", "Content-Security-Policy",
 HEADER_ARGS = {"Strict-Transport-Security": HSTS_ARGS,
         "Upgrade-Insecure-Requests": UIR_ARGS}
 
+def os_constant(key):
+    os_info = le_util.get_os_info()
+    try:
+        constants = CLI_DEFAULTS[os_info[0].lower()]
+    except KeyError:
+        constants = CLI_DEFAULTS["debian"]
+    return constants[key]