diff --git a/etc/ironic/ironic.conf.sample b/etc/ironic/ironic.conf.sample
index 17cd31bc2f..53b378dab9 100644
--- a/etc/ironic/ironic.conf.sample
+++ b/etc/ironic/ironic.conf.sample
@@ -951,10 +951,10 @@
 #pxe_bootfile_name=pxelinux.0
 
 # Maximum size (in MiB) of cache for master images, including
-# those in use (integer value)
-#image_cache_size=1024
+# those in use. (integer value)
+#image_cache_size=20480
 
-# Maximum TTL (in minutes) for old master images in cache
+# Maximum TTL (in minutes) for old master images in cache.
 # (integer value)
 #image_cache_ttl=60
 
diff --git a/ironic/drivers/modules/pxe.py b/ironic/drivers/modules/pxe.py
index 04de94f097..8541c32ed5 100644
--- a/ironic/drivers/modules/pxe.py
+++ b/ironic/drivers/modules/pxe.py
@@ -69,12 +69,13 @@ pxe_opts = [
                default='pxelinux.0',
                help='Neutron bootfile DHCP parameter.'),
     cfg.IntOpt('image_cache_size',
-               default=1024,
+               default=20480,
                help='Maximum size (in MiB) of cache for master images, '
-               'including those in use'),
+               'including those in use.'),
     cfg.IntOpt('image_cache_ttl',
                default=60,
-               help='Maximum TTL (in minutes) for old master images in cache'),
+               help='Maximum TTL (in minutes) for old master images in '
+               'cache.'),
     ]
 
 LOG = logging.getLogger(__name__)