diff --git a/wp-admin/admin-ajax.php b/wp-admin/admin-ajax.php
index 3829adf76d..90b3353117 100644
--- a/wp-admin/admin-ajax.php
+++ b/wp-admin/admin-ajax.php
@@ -91,6 +91,8 @@ case 'wp-compression-test' :
 		 	echo $test_str;
 		 	die;
 		 } elseif ( 2 == $_GET['test'] ) {
+			if ( !isset($_SERVER['HTTP_ACCEPT_ENCODING']) )
+				die('-1');
 			if ( false !== strpos( strtolower($_SERVER['HTTP_ACCEPT_ENCODING']), 'deflate') && function_exists('gzdeflate') && ! $force_gzip ) {
 				header('Content-Encoding: deflate');
 				$out = gzdeflate( $test_str, 1 );
diff --git a/wp-admin/load-scripts.php b/wp-admin/load-scripts.php
index 957a8cb480..b01ba30e2c 100644
--- a/wp-admin/load-scripts.php
+++ b/wp-admin/load-scripts.php
@@ -127,7 +127,7 @@ header('Content-Type: application/x-javascript; charset=UTF-8');
 header('Expires: ' . gmdate( "D, d M Y H:i:s", time() + $expires_offset ) . ' GMT');
 header("Cache-Control: public, max-age=$expires_offset");
 
-if ( $compress && ! ini_get('zlib.output_compression') && 'ob_gzhandler' != ini_get('output_handler') ) {
+if ( $compress && ! ini_get('zlib.output_compression') && 'ob_gzhandler' != ini_get('output_handler') && isset($_SERVER['HTTP_ACCEPT_ENCODING']) ) {
 	header('Vary: Accept-Encoding'); // Handle proxies
 	if ( false !== strpos( strtolower($_SERVER['HTTP_ACCEPT_ENCODING']), 'deflate') && function_exists('gzdeflate') && ! $force_gzip ) {
 		header('Content-Encoding: deflate');
diff --git a/wp-admin/load-styles.php b/wp-admin/load-styles.php
index 93584274d9..1e10c47a94 100644
--- a/wp-admin/load-styles.php
+++ b/wp-admin/load-styles.php
@@ -137,7 +137,7 @@ header('Content-Type: text/css');
 header('Expires: ' . gmdate( "D, d M Y H:i:s", time() + $expires_offset ) . ' GMT');
 header("Cache-Control: public, max-age=$expires_offset");
 
-if ( $compress && ! ini_get('zlib.output_compression') && 'ob_gzhandler' != ini_get('output_handler') ) {
+if ( $compress && ! ini_get('zlib.output_compression') && 'ob_gzhandler' != ini_get('output_handler') && isset($_SERVER['HTTP_ACCEPT_ENCODING']) ) {
 	header('Vary: Accept-Encoding'); // Handle proxies
 	if ( false !== strpos( strtolower($_SERVER['HTTP_ACCEPT_ENCODING']), 'deflate') && function_exists('gzdeflate') && ! $force_gzip ) {
 		header('Content-Encoding: deflate');
diff --git a/wp-includes/js/tinymce/wp-tinymce.php b/wp-includes/js/tinymce/wp-tinymce.php
index efd2f5985f..b2ef19d445 100644
--- a/wp-includes/js/tinymce/wp-tinymce.php
+++ b/wp-includes/js/tinymce/wp-tinymce.php
@@ -1,4 +1,10 @@
 <?php
+/**
+ * Disable error reporting
+ *
+ * Set this to error_reporting( E_ALL ) or error_reporting( E_ALL | E_STRICT ) for debugging
+ */
+error_reporting(0);
 
 $basepath = dirname(__FILE__);
 
@@ -20,7 +26,9 @@ header('Vary: Accept-Encoding'); // Handle proxies
 header('Expires: ' . gmdate( "D, d M Y H:i:s", time() + $expires_offset ) . ' GMT');
 header("Cache-Control: public, max-age=$expires_offset");
 
-if ( isset($_GET['c']) && 1 == $_GET['c'] && false !== strpos( strtolower($_SERVER['HTTP_ACCEPT_ENCODING']), 'gzip') && ( $file = get_file($basepath . '/wp-tinymce.js.gz') ) ) {
+if ( isset($_GET['c']) && 1 == $_GET['c'] && isset($_SERVER['HTTP_ACCEPT_ENCODING'])
+	&& false !== strpos( strtolower($_SERVER['HTTP_ACCEPT_ENCODING']), 'gzip') && ( $file = get_file($basepath . '/wp-tinymce.js.gz') ) ) {
+
 	header('Content-Encoding: gzip');
 	echo $file;
 } else {