diff --git a/readme.txt b/readme.txt
index 0ece9ad..b2280e7 100644
--- a/readme.txt
+++ b/readme.txt
@@ -4,7 +4,7 @@ Donate link: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_i
 Tags: cache, page cache, full page cache, nginx, memcached, apc, speed
 Requires at least: 3.0
 Tested up to: 4.2.1
-Stable tag: 1.8.2
+Stable tag: 1.8.3
 License: GPLv3
 License URI: http://www.gnu.org/licenses/gpl-3.0.html
 
@@ -125,6 +125,11 @@ Version numbering logic:
 * every .B version indicates new features.
 * every ..C indicates bugfixes for A.B version.
 
+= 1.8.3 =
+*2015-05-07*
+
+* small change in key creation: prefix is kept in front of sha1 hashes for debugging purposes
+
 = 1.8.2 =
 *2015-04-30*
 
diff --git a/wp-ffpc-backend.php b/wp-ffpc-backend.php
index 4aae169..9e34e53 100644
--- a/wp-ffpc-backend.php
+++ b/wp-ffpc-backend.php
@@ -139,10 +139,11 @@ class WP_FFPC_Backend {
 		$urimap = $customUrimap ?: $this->urimap;
 
 		$key_base = self::map_urimap($urimap, $this->options['key']);
-		/* data is string only with content, meta is not used in nginx */
-		$key = $prefix . $key_base;
+
 		if ( isset($this->options['hashkey']) && $this->options['hashkey'] == true)
-			$key = sha1 ($prefix . $key_base );
+			$key_base = sha1($key_base);
+
+		$key = $prefix . $key_base;
 
 		$this->log ( sprintf( __translate__( 'original key configuration: %s', $this->plugin_constant ),  $this->options['key'] ) );
 		$this->log ( sprintf( __translate__( 'setting key for: %s', $this->plugin_constant ),  $key_base ) );
diff --git a/wp-ffpc-class.php b/wp-ffpc-class.php
index 0a3b218..57285b0 100644
--- a/wp-ffpc-class.php
+++ b/wp-ffpc-class.php
@@ -576,7 +576,7 @@ class WP_FFPC extends WP_FFPC_ABSTRACT {
 				</dt>
 				<dd>
 					<input type="checkbox" name="hashkey" id="hashkey" value="1" <?php checked($this->options['hashkey'],true); ?> />
-					<span class="description"><?php _e('Occasionally URL can be too long to be used as key for the backend storage, especially with memcached. Turn on this feature to use SHA1 hash of the URL as key instead. Please be aware that you have to add ( or uncomment ) a line in nginx if you want nginx to fetch the data directly; for details, please see the nginx example tab.', $this->plugin_constant); ?>
+					<span class="description"><?php _e('Occasionally URL can be too long to be used as key for the backend storage, especially with memcached. Turn on this feature to use SHA1 hash of the URL as key instead. Please be aware that you have to add ( or uncomment ) a line and a <strong>module</strong> in nginx if you want nginx to fetch the data directly; for details, please see the nginx example tab.', $this->plugin_constant); ?>
 				</dd>
 
 
@@ -745,6 +745,7 @@ class WP_FFPC extends WP_FFPC_ABSTRACT {
 
 			<fieldset id="<?php echo $this->plugin_constant ?>-nginx">
 			<legend><?php _e('Sample config for nginx to utilize the data entries', $this->plugin_constant); ?></legend>
+			<div class="update-nag"><strong>In case you are about to use nginx to fetch memcached entries directly and to use SHA1 hash keys, you will need an nginx version compiled with <a href="http://wiki.nginx.org/HttpSetMiscModule">HttpSetMiscModule</a>. Otherwise set_sha1 function is not available in nginx.</strong></div>
 			<pre><?php echo $this->nginx_example(); ?></pre>
 			</fieldset>
 
@@ -1019,11 +1020,20 @@ class WP_FFPC extends WP_FFPC_ABSTRACT {
 		/* read the sample file */
 		$nginx = file_get_contents ( $this->nginx_sample );
 
+		if ( isset($this->options['hashkey']) && $this->options['hashkey'] == true )
+			$mckeys = 'set_sha1 $memcached_sha1_key $memcached_raw_key;
+			set $memcached_key DATAPREFIX$memcached_sha1_key;';
+		else
+			$mckeys = 'set $memcached_key DATAPREFIX$memcached_raw_key;';
+
+		$nginx = str_replace ( 'HASHEDORNOT' , $mckeys , $nginx );
+
 		/* replace the data prefix with the configured one */
-		$to_replace = array ( 'DATAPREFIX' , 'SERVERROOT', 'SERVERLOG' );
-		$replace_with = array ( $this->options['prefix_data'] . $this->options['key'] , ABSPATH, $_SERVER['SERVER_NAME'] );
+		$to_replace = array ( 'DATAPREFIX' , 'KEYFORMAT',  'SERVERROOT', 'SERVERLOG' );
+		$replace_with = array ( $this->options['prefix_data'],  $this->options['key'] , ABSPATH, $_SERVER['SERVER_NAME'] );
 		$nginx = str_replace ( $to_replace , $replace_with , $nginx );
 
+
 		/* set upstream servers from configured servers, best to get from the actual backend */
 		$servers = $this->backend->get_servers();
 		$nginx_servers = '';
diff --git a/wp-ffpc-nginx-sample.conf b/wp-ffpc-nginx-sample.conf
index ce6a628..000fc06 100644
--- a/wp-ffpc-nginx-sample.conf
+++ b/wp-ffpc-nginx-sample.conf
@@ -70,10 +70,11 @@ MEMCACHED_SERVERS
 			#fastcgi_param	SSL_CLIENT_VERIFY		$ssl_client_verify if_not_empty;
 
 			default_type text/html;
-			set $memcached_raw_key data-$scheme://$host$request_uri;
-			# uncomment the following line if you have enabled
-			# sha1 hash option
-			# set_sha1 $memcached_key $memcached_raw_key;
+
+			set $memcached_raw_key KEYFORMAT;
+
+			HASHEDORNOT
+
 			set $memcached_request 1;
 
 			if ($request_method = POST ) {
diff --git a/wp-ffpc.php b/wp-ffpc.php
index 7efb1c2..de11818 100644
--- a/wp-ffpc.php
+++ b/wp-ffpc.php
@@ -3,7 +3,7 @@
 Plugin Name: WP-FFPC
 Plugin URI: https://github.com/petermolnar/wp-ffpc
 Description: WordPress in-memory full page cache plugin
-Version: 1.8.2
+Version: 1.8.3
 Author: Peter Molnar <hello@petermolnar.eu>
 Author URI: http://petermolnar.eu/
 License: GPLv3