diff --git a/src/WordPress/AsyncHttp/Client.php b/src/WordPress/AsyncHttp/Client.php
index 3af08da5..1681a240 100644
--- a/src/WordPress/AsyncHttp/Client.php
+++ b/src/WordPress/AsyncHttp/Client.php
@@ -708,7 +708,7 @@ private function parse_http_headers( string $headers ) {
 		$status  = explode( ' ', $status );
 		$status  = array(
 			'protocol' => $status[0],
-			'code'     => $status[1],
+			'code'     => (int) $status[1],
 			'message'  => $status[2],
 		);
 		$headers = array();
@@ -822,17 +822,29 @@ static private function prepare_request_headers( Request $request ) {
 		$path  = ( isset( $parts['path'] ) ? $parts['path'] : '/' ) . ( isset( $parts['query'] ) ? '?' . $parts['query'] : '' );
 
 		$headers = [
-			"Host"            => $host,
-			"User-Agent"      => "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82 Safari/537.36",
-			"Accept"          => "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
-			"Accept-Encoding" => "gzip",
-			"Accept-Language" => "en-US,en;q=0.9",
-			"Connection"      => "close",
+			"host"            => $host,
+			"user-agent"      => "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82 Safari/537.36",
+			"accept"          => "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
+			"accept-language" => "en-US,en;q=0.9",
+			"connection"      => "close",
 		];
 		foreach ( $request->headers as $k => $v ) {
 			$headers[ $k ] = $v;
 		}
 
+		/**
+		 * Disable the gzip transfer compression when requesting a byte range.
+		 *
+		 * When we're requesting a byte range AND gzipped transfer encoding,
+		 * our intention is to get compressed bytes 0-X of the original file.
+		 *
+		 * However, some servers will compress the file first, and then return
+		 * the compressed bytes 0-X. The result is both unpredictable and impossible
+		 * to decompress.
+		 */
+		if(!array_key_exists('range', $headers)) {
+			$headers['accept-encoding'] = 'gzip';
+		}
 
 		$request_parts = array(
 			"$request->method $path HTTP/$request->http_version",
diff --git a/src/WordPress/AsyncHttp/Request.php b/src/WordPress/AsyncHttp/Request.php
index 2320fd37..4e10dbb3 100644
--- a/src/WordPress/AsyncHttp/Request.php
+++ b/src/WordPress/AsyncHttp/Request.php
@@ -50,7 +50,7 @@ public function __construct( string $url, $request_info = array() ) {
 		$this->is_ssl = strpos( $url, 'https://' ) === 0;
 
 		$this->method             = $request_info['method'];
-		$this->headers            = $request_info['headers'];
+		$this->headers            = array_change_key_case($request_info['headers'], CASE_LOWER);
 		$this->upload_body_stream = $request_info['body_stream'];
 		$this->http_version       = $request_info['http_version'];
 		$this->redirected_from    = $request_info['redirected_from'];
diff --git a/src/WordPress/Zip/NewZipStreamReader.php b/src/WordPress/Zip/NewZipStreamReader.php
index a7197d05..b49552b2 100644
--- a/src/WordPress/Zip/NewZipStreamReader.php
+++ b/src/WordPress/Zip/NewZipStreamReader.php
@@ -8,6 +8,7 @@
  * 
  * @TODO: Replace ZipStreamReader with this class once the consumers of
  *        ZipStreamReader have been updated to use the new interface.
+ * @TODO: Replace fopen() et al. with the Stream interface (append_bytes() etc.)
  */
 class NewZipStreamReader {