diff --git a/lib/x11/unpackstream.js b/lib/x11/unpackstream.js
index ed7e5be..1e963b6 100644
--- a/lib/x11/unpackstream.js
+++ b/lib/x11/unpackstream.js
@@ -244,6 +244,7 @@ UnpackStream.prototype.pack = function(format, arguments)
                 var n = arguments[arg++];
                 buf[offset++] = n;
                 break;
+            case 's': // TODO: implement signed INT16!!!
             case 'S':
                 var n = arguments[arg++];
                 buf[offset++] = n & 0xff;
@@ -256,11 +257,17 @@ UnpackStream.prototype.pack = function(format, arguments)
                 buf[offset++] = (n >> 16) & 0xff;
                 buf[offset++] = (n >> 24) & 0xff;
                 break;
-            case 'a':  // string
+            case 'a':  // string or buffer
                 var str = arguments[arg++];
-                // TODO: buffer.write could be faster
-                for (var c = 0; c < str.length; ++c)
-                    buf[offset++] = str.charCodeAt(c);
+                if (Buffer.isBuffer(str))
+                {
+                    str.copy(buf, offset);
+                    offset += str.length;
+                } else {
+                    // TODO: buffer.write could be faster
+                    for (var c = 0; c < str.length; ++c)
+                        buf[offset++] = str.charCodeAt(c);
+                }
                 break;
             case 'p':  // padded string
                 var str = arguments[arg++];