diff --git a/system/libraries/Cache/drivers/Cache_apc.php b/system/libraries/Cache/drivers/Cache_apc.php
index dd18e7b..07ea8f4 100644
--- a/system/libraries/Cache/drivers/Cache_apc.php
+++ b/system/libraries/Cache/drivers/Cache_apc.php
@@ -49,6 +49,24 @@
 class CI_Cache_apc extends CI_Driver {
 
 	/**
+	 * Class constructor
+	 *
+	 * Only present so that an error message is logged
+	 * if APC is not available.
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		if ( ! $this->is_supported())
+		{
+			log_message('error', 'Cache: Failed to initialize APC; extension not loaded/enabled?');
+		}
+	}
+
+	// ------------------------------------------------------------------------
+
+	/**
 	 * Get
 	 *
 	 * Look for a value in the cache. If it exists, return the data
@@ -198,13 +216,6 @@
 	 */
 	public function is_supported()
 	{
-		if ( ! extension_loaded('apc') OR ! ini_get('apc.enabled'))
-		{
-			log_message('debug', 'The APC PHP extension must be loaded to use APC Cache.');
-			return FALSE;
-		}
-
-		return TRUE;
+		return (extension_loaded('apc') && ini_get('apc.enabled'));
 	}
-
 }
diff --git a/system/libraries/Cache/drivers/Cache_memcached.php b/system/libraries/Cache/drivers/Cache_memcached.php
index c44958b..7e67fc4 100644
--- a/system/libraries/Cache/drivers/Cache_memcached.php
+++ b/system/libraries/Cache/drivers/Cache_memcached.php
@@ -107,6 +107,7 @@
 		else
 		{
 			log_message('error', 'Cache: Failed to create Memcache(d) object; extension not loaded?');
+			return;
 		}
 
 		foreach ($this->_memcache_conf as $cache_server)
diff --git a/system/libraries/Cache/drivers/Cache_redis.php b/system/libraries/Cache/drivers/Cache_redis.php
index 81b49e2..e9194a4 100644
--- a/system/libraries/Cache/drivers/Cache_redis.php
+++ b/system/libraries/Cache/drivers/Cache_redis.php
@@ -91,6 +91,12 @@
 	 */
 	public function __construct()
 	{
+		if ( ! $this->is_supported())
+		{
+			log_message('error', 'Cache: Failed to create Redis object; extension not loaded?');
+			return;
+		}
+
 		$config = array();
 		$CI =& get_instance();
 
diff --git a/system/libraries/Cache/drivers/Cache_wincache.php b/system/libraries/Cache/drivers/Cache_wincache.php
index f660805..d6a0d4f 100644
--- a/system/libraries/Cache/drivers/Cache_wincache.php
+++ b/system/libraries/Cache/drivers/Cache_wincache.php
@@ -52,6 +52,24 @@
 class CI_Cache_wincache extends CI_Driver {
 
 	/**
+	 * Class constructor
+	 *
+	 * Only present so that an error message is logged
+	 * if APC is not available.
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		if ( ! $this->is_supported())
+		{
+			log_message('error', 'Cache: Failed to initialize Wincache; extension not loaded/enabled?');
+		}
+	}
+
+	// ------------------------------------------------------------------------
+
+	/**
 	 * Get
 	 *
 	 * Look for a value in the cache. If it exists, return the data,
@@ -194,13 +212,6 @@
 	 */
 	public function is_supported()
 	{
-		if ( ! extension_loaded('wincache') OR ! ini_get('wincache.ucenabled'))
-		{
-			log_message('debug', 'The Wincache PHP extension must be loaded to use Wincache Cache.');
-			return FALSE;
-		}
-
-		return TRUE;
+		return (extension_loaded('wincache') && ini_get('wincache.ucenabled'));
 	}
-
 }
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 888ae5f..52e8d13 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -44,6 +44,8 @@
 -  Fixed a bug where :doc:`Database <database/index>` transactions didn't work with the 'ibase' driver.
 -  Fixed a bug (#4475) - :doc:`Security Library <libraries/security>` method ``strip_image_tags()`` preserves only the first URL character from non-quoted *src* attributes.
 -  Fixed a bug where :doc:`Profiler Library <general/profiling>` didn't apply ``htmlspecialchars()`` to all displayed inputs.
+-  Fixed a bug (#4277) - :doc:`Cache Library <libraries/caching>` triggered fatal errors if accessing the Memcache(d) and/or Redis driver and they are not available on the system.
+-  Fixed a bug where :doc:`Cache Library <libraries/caching>` method ``is_supported()`` logged an error message on when it returns ``FALSE`` for the APC and Wincache drivers.
 
 Version 3.0.4
 =============