Index: wp-includes/class-http.php
===================================================================
--- wp-includes/class-http.php	(revision 26111)
+++ wp-includes/class-http.php	(working copy)
@@ -1108,7 +1108,7 @@
 	function request($url, $args = array()) {
 		$defaults = array(
 			'method' => 'GET', 'timeout' => 5,
-			'redirection' => 5, 'httpversion' => '1.0',
+			'redirection' => 5, 'httpversion' => null,
 			'blocking' => true,
 			'headers' => array(), 'body' => null, 'cookies' => array()
 		);
@@ -1220,10 +1220,13 @@
 			curl_setopt( $handle, CURLOPT_HTTPHEADER, $headers );
 		}
 
-		if ( $r['httpversion'] == '1.0' )
-			curl_setopt( $handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_0 );
-		else
-			curl_setopt( $handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1 );
+		// If the version is not set explicitly, let cURL figure things out
+		if ( !empty( $r['httpversion'] ) ) {
+			if ( $r['httpversion'] == '1.0' )
+				curl_setopt( $handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_0 );
+			else
+				curl_setopt( $handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1 );
+		}
 
 		// Cookies are not handled by the HTTP API currently. Allow for plugin authors to handle it
 		// themselves... Although, it is somewhat pointless without some reference.