diff --git a/boot/boot.js b/boot/boot.js
index d9719ed50..284d58db9 100644
--- a/boot/boot.js
+++ b/boot/boot.js
@@ -1220,10 +1220,14 @@ $tw.Wiki.prototype.processSafeMode = function() {
 /*
 Extracts tiddlers from a typed block of text, specifying default field values
 */
-$tw.Wiki.prototype.deserializeTiddlers = function(type,text,srcFields) {
+$tw.Wiki.prototype.deserializeTiddlers = function(type,text,srcFields,options) {
 	srcFields = srcFields || Object.create(null);
-	var deserializer = $tw.Wiki.tiddlerDeserializerModules[type],
+	options = options || {};
+	var deserializer = $tw.Wiki.tiddlerDeserializerModules[options.deserializer],
 		fields = Object.create(null);
+	if(!deserializer) {
+		deserializer = $tw.Wiki.tiddlerDeserializerModules[type];
+	}
 	if(!deserializer && $tw.utils.getFileExtensionInfo(type)) {
 		// If we didn't find the serializer, try converting it from an extension to a content type
 		type = $tw.utils.getFileExtensionInfo(type).type;
diff --git a/core/modules/widgets/dropzone.js b/core/modules/widgets/dropzone.js
index 08d875c39..d732fb97d 100644
--- a/core/modules/widgets/dropzone.js
+++ b/core/modules/widgets/dropzone.js
@@ -104,7 +104,10 @@ DropZoneWidget.prototype.handleDragLeaveEvent  = function(event) {
 };
 
 DropZoneWidget.prototype.handleDropEvent  = function(event) {
-	var self = this;
+	var self = this,
+		readFileCallback = function(tiddlerFieldsArray) {
+			self.dispatchEvent({type: "tm-import-tiddlers", param: JSON.stringify(tiddlerFieldsArray)});
+		};
 	this.leaveDrag(event);
 	// Check for being over a TEXTAREA or INPUT
 	if(["TEXTAREA","INPUT"].indexOf(event.target.tagName) !== -1) {
@@ -121,15 +124,14 @@ DropZoneWidget.prototype.handleDropEvent  = function(event) {
 	// Import any files in the drop
 	var numFiles = 0;
 	if(dataTransfer.files) {
-		numFiles = this.wiki.readFiles(dataTransfer.files,function(tiddlerFieldsArray) {
-			self.dispatchEvent({type: "tm-import-tiddlers", param: JSON.stringify(tiddlerFieldsArray)});
+		numFiles = this.wiki.readFiles(dataTransfer.files,{
+			callback: readFileCallback,
+			deserializer: this.dropzoneDeserializer
 		});
 	}
 	// Try to import the various data types we understand
 	if(numFiles === 0) {
-		$tw.utils.importDataTransfer(dataTransfer,this.wiki.generateNewTitle("Untitled"),function(fieldsArray) {
-			self.dispatchEvent({type: "tm-import-tiddlers", param: JSON.stringify(fieldsArray)});
-		});
+		$tw.utils.importDataTransfer(dataTransfer,this.wiki.generateNewTitle("Untitled"),readFileCallback);
 	}
 	// Tell the browser that we handled the drop
 	event.preventDefault();
@@ -138,6 +140,10 @@ DropZoneWidget.prototype.handleDropEvent  = function(event) {
 };
 
 DropZoneWidget.prototype.handlePasteEvent  = function(event) {
+	var self = this,
+		readFileCallback = function(tiddlerFieldsArray) {
+			self.dispatchEvent({type: "tm-import-tiddlers", param: JSON.stringify(tiddlerFieldsArray)});
+		};
 	// Let the browser handle it if we're in a textarea or input box
 	if(["TEXTAREA","INPUT"].indexOf(event.target.tagName) == -1) {
 		var self = this,
@@ -147,8 +153,9 @@ DropZoneWidget.prototype.handlePasteEvent  = function(event) {
 			var item = items[t];
 			if(item.kind === "file") {
 				// Import any files
-				this.wiki.readFile(item.getAsFile(),function(tiddlerFieldsArray) {
-					self.dispatchEvent({type: "tm-import-tiddlers", param: JSON.stringify(tiddlerFieldsArray)});
+				this.wiki.readFile(item.getAsFile(),{
+					callback: readFileCallback,
+					deserializer: this.dropzoneDeserializer
 				});
 			} else if(item.kind === "string") {
 				// Create tiddlers from string items
@@ -176,6 +183,7 @@ DropZoneWidget.prototype.handlePasteEvent  = function(event) {
 Compute the internal state of the widget
 */
 DropZoneWidget.prototype.execute = function() {
+	this.dropzoneDeserializer = this.getAttribute("deserializer");
 	// Make child widgets
 	this.makeChildWidgets();
 };
diff --git a/core/modules/wiki.js b/core/modules/wiki.js
index 1d077fd67..b2dbed5c9 100755
--- a/core/modules/wiki.js
+++ b/core/modules/wiki.js
@@ -1125,16 +1125,24 @@ exports.checkTiddlerText = function(title,targetText,options) {
 /*
 Read an array of browser File objects, invoking callback(tiddlerFieldsArray) once they're all read
 */
-exports.readFiles = function(files,callback) {
+exports.readFiles = function(files,options) {
+	var callback;
+	if(typeof options === "function") {
+		callback = options;
+		options = {};
+	} else {
+		callback = options.callback;
+	}
 	var result = [],
-		outstanding = files.length;
-	for(var f=0; f<files.length; f++) {
-		this.readFile(files[f],function(tiddlerFieldsArray) {
+		outstanding = files.length,
+		readFileCallback = function(tiddlerFieldsArray) {
 			result.push.apply(result,tiddlerFieldsArray);
 			if(--outstanding === 0) {
 				callback(result);
 			}
-		});
+		};
+	for(var f=0; f<files.length; f++) {
+		this.readFile(files[f],Object.assign({},options,{callback: readFileCallback}));
 	}
 	return files.length;
 };
@@ -1142,7 +1150,14 @@ exports.readFiles = function(files,callback) {
 /*
 Read a browser File object, invoking callback(tiddlerFieldsArray) with an array of tiddler fields objects
 */
-exports.readFile = function(file,callback) {
+exports.readFile = function(file,options) {
+	var callback;
+	if(typeof options === "function") {
+		callback = options;
+		options = {};
+	} else {
+		callback = options.callback;
+	}
 	// Get the type, falling back to the filename extension
 	var self = this,
 		type = file.type;
@@ -1183,7 +1198,7 @@ exports.readFile = function(file,callback) {
 			});
 		} else {
 			// Otherwise, just try to deserialise any tiddlers in the file
-			callback(self.deserializeTiddlers(type,text,tiddlerFields));
+			callback(self.deserializeTiddlers(type,text,tiddlerFields,{deserializer: options.deserializer}));
 		}
 	};
 	// Kick off the read
diff --git a/editions/tw5.com/tiddlers/widgets/DropzoneWidget.tid b/editions/tw5.com/tiddlers/widgets/DropzoneWidget.tid
index 29813f65b..7d8ff773b 100644
--- a/editions/tw5.com/tiddlers/widgets/DropzoneWidget.tid
+++ b/editions/tw5.com/tiddlers/widgets/DropzoneWidget.tid
@@ -1,6 +1,6 @@
 caption: dropzone
 created: 20131024141900000
-modified: 20170328173334805
+modified: 20170712153850528
 tags: Widgets
 title: DropzoneWidget
 type: text/vnd.tiddlywiki
@@ -13,7 +13,12 @@ It sends a [[WidgetMessage: tm-import-tiddlers]] carrying a JSON representation
 
 ! Content and Attributes
 
-The dropzone widget has no attributes, and displays any contained content within the dropzone.
+|!Attribute |!Description |
+|deserializer |Optional name of deserializer to be used (by default the deserializer is derived from the file extension) |
+
+The list of available deserializers can be inspected by executing `Object.keys($tw.Wiki.tiddlerDeserializerModules).sort().join("\n")` in the browser JavaScript console.
+
+The dropzone widget displays any contained content within the dropzone.
 
 ! Display