diff --git a/docs/simplesamlphp-changelog.md b/docs/simplesamlphp-changelog.md
index 019956b4441b61669036835907c6458d30fc8a48..ca37526e5fc9d78e9d8b64a3af7be0a847cb66aa 100644
--- a/docs/simplesamlphp-changelog.md
+++ b/docs/simplesamlphp-changelog.md
@@ -16,6 +16,8 @@ Released TBD
   * Improve 'update or insert' handling for different SQL drivers
   * The default algorithm within the TimeLimitedToken-class has been bumped from SHA-1 to SHA-256
     as announced by deprecation notice in 1.15-RC1
+  * Most modules have been externalized. They will not be included in our future releases by default,
+    but will be easily installable using Composer.
 
 ### metarefresh
   * The algorithm to compute the fingerprint of the certificate that signed
@@ -40,6 +42,8 @@ Released TBD
   * Setting 'privacypolicy' in metadata-files will be removed in a future release. It was only used
     by the consent-module, which supports UIInfo's PrivacyStatementURL.
     See https://simplesamlphp.org/docs/stable/simplesamlphp-metadata-extensions-ui on how to configure this.
+  * The use of the PHP memcache-extension was deprecated in favour of memcached-extension.
+    The former is considered abandoned and it's safe use can no longer be guaranteed.
 
 ## Version 1.17.5
 
diff --git a/docs/simplesamlphp-upgrade-notes-1.18.md b/docs/simplesamlphp-upgrade-notes-1.18.md
new file mode 100644
index 0000000000000000000000000000000000000000..515ede778f53fdbfe881718fc05c282d9a203b1b
--- /dev/null
+++ b/docs/simplesamlphp-upgrade-notes-1.18.md
@@ -0,0 +1,7 @@
+Upgrade notes for SimpleSAMLphp 1.18
+====================================
+
+The minimum PHP version required is now PHP 5.6.
+
+The use of the PHP Memcache-extension was deprecated in favour of the Memcached-extension.
+
diff --git a/lib/SimpleSAML/Memcache.php b/lib/SimpleSAML/Memcache.php
index 0d4a11eded06d535a064f07d09f5f8edab44548a..904649775459233862a753dd2c84bc10d630e893 100644
--- a/lib/SimpleSAML/Memcache.php
+++ b/lib/SimpleSAML/Memcache.php
@@ -315,6 +315,8 @@ class Memcache
             throw new \Exception(
                 'Missing Memcached implementation. You must install either the Memcache or Memcached extension.'
             );
+        } elseif (strtolower($class) === '\memcache') {
+            Logger::warning("The use of PHP-extension memcache is deprecated. Please migrate to the memcached extension.");
         }
         self::$extension = strtolower($class);