diff --git a/lib/FileAPI.Form.js b/lib/FileAPI.Form.js
index d49c178a..fa5586e2 100644
--- a/lib/FileAPI.Form.js
+++ b/lib/FileAPI.Form.js
@@ -113,7 +113,7 @@
 				    data.params.push(encodeURIComponent(file.name) + "=" + encodeURIComponent(file.blob));
 				}
 				data.start = -1;
-				data.end = -1;
+				data.end = data.file.FileAPIReadPosition || -1;
 				data.retry = 0;
 			});
 		},
diff --git a/lib/FileAPI.XHR.js b/lib/FileAPI.XHR.js
index 0787896b..8978c3c0 100644
--- a/lib/FileAPI.XHR.js
+++ b/lib/FileAPI.XHR.js
@@ -70,6 +70,7 @@
 		},
 
 		_send: function (options, data){
+
 			var _this = this, xhr, uid = _this.uid, url = options.url;
 
 			api.log('XHR._send:', data);
@@ -193,10 +194,10 @@
 									options.pause(data.file, options);
 
 									// smart restart if server reports about the last known byte
-									var lkb = xhr.getResponseHeader('X-Last-Known-Byte');
+									var lkb = parseInt(xhr.getResponseHeader('X-Last-Known-Byte'), 10);
 									api.log("X-Last-Known-Byte: " + lkb);
 									if (lkb) {
-										data.end = parseInt(lkb);
+										data.end = lkb;
 									} else {
 										data.end = data.start - 1;
 									}
@@ -217,6 +218,15 @@
 									_this.end(xhr.status);
 								} else {
 									// next chunk
+
+									// shift position if server reports about the last known byte
+									var lkb = parseInt(xhr.getResponseHeader('X-Last-Known-Byte'), 10);
+									api.log("X-Last-Known-Byte: " + lkb);
+									if (lkb) {
+										data.end = lkb;
+									}
+									data.file.FileAPIReadPosition = data.end;
+
 									setTimeout(function () {
 									    _this._send(options, data);
 									}, 0);