diff --git a/core/modules/filters/unknown.js b/core/modules/filters/unknown.js
index 81f868427..c52045474 100644
--- a/core/modules/filters/unknown.js
+++ b/core/modules/filters/unknown.js
@@ -24,30 +24,15 @@ exports["[unknown]"] = function(source,operator,options) {
 		var customDefinition = options.widget && options.widget.getVariableInfo && options.widget.getVariableInfo(operator.operator);
 		if(customDefinition && customDefinition.srcVariable && customDefinition.srcVariable.isFunctionDefinition) {
 			var variables = Object.create(null);
+			// Go through each of the defined parameters, and make a variable with the value of the corresponding operand
 			$tw.utils.each(customDefinition.srcVariable.params,function(param,index) {
-				var value = operator.operands[index];
+				var value = operator.operands["" + index];
 				if(value === undefined) {
 					value = param["default"] || "";
 				}
 				variables[param.name] = value;
 			});
-			var getVariable = function(name,opts) {
-				if(name in variables) {
-					return variables[name];
-				} else {
-					return options.widget.getVariable(name,opts);
-				};
-			};
-			var getVariableInfo = function(name,opts) {
-				if(name in variables) {
-					return {
-						text: variables[name]
-					};
-				} else {
-					return options.widget.getVariableInfo(name,opts);
-				};
-			}
-			var list = options.wiki.filterTiddlers(customDefinition.srcVariable.value,{getVariable: getVariable,getVariableInfo: getVariableInfo},source);
+			var list = options.wiki.filterTiddlers(customDefinition.srcVariable.value,options.widget.makeFakeWidgetWithVariables(variables),source);
 			if(operator.prefix === "!") {
 				var results = [];
 				source(function(tiddler,title) {
diff --git a/core/modules/widgets/widget.js b/core/modules/widgets/widget.js
index 627c3490c..444e0ce87 100755
--- a/core/modules/widgets/widget.js
+++ b/core/modules/widgets/widget.js
@@ -275,6 +275,32 @@ Widget.prototype.getStateQualifier = function(name) {
 	}
 };
 
+/*
+Make a fake widget with specified variables, suitable for variable lookup in filters
+*/
+Widget.prototype.makeFakeWidgetWithVariables = function(variables) {
+	var self = this;
+	return {
+		getVariable: function(name,opts) {
+			if(name in variables) {
+				return variables[name];
+			} else {
+				return self.getVariable(name,opts);
+			};
+		},
+		getVariableInfo: function(name,opts) {
+			if(name in variables) {
+				return {
+					text: variables[name]
+				};
+			} else {
+				return self.getVariableInfo(name,opts);
+			};
+		},
+		makeFakeWidgetWithVariables: self.makeFakeWidgetWithVariables
+	};
+};
+
 /*
 Compute the current values of the attributes of the widget. Returns a hashmap of the names of the attributes that have changed.
 Options include:
@@ -300,13 +326,27 @@ Widget.prototype.computeAttributes = function(options) {
 };
 
 Widget.prototype.computeAttribute = function(attribute) {
-	var value;
+	var self = this,
+		value;
 	if(attribute.type === "filtered") {
 		value = this.wiki.filterTiddlers(attribute.filter,this)[0] || "";
 	} else if(attribute.type === "indirect") {
 		value = this.wiki.getTextReference(attribute.textReference,"",this.getVariable("currentTiddler"));
 	} else if(attribute.type === "macro") {
-		value = this.getVariable(attribute.value.name,{params: attribute.value.params});
+		var variableInfo = this.getVariableInfo(attribute.value.name,{params: attribute.value.params});
+		if(variableInfo.srcVariable && variableInfo.srcVariable.isFunctionDefinition) {
+			// It's a function definition
+			var variables = Object.create(null);
+			// Go through each of the defined parameters, and make a variable with the value of the corresponding provided parameter
+			var params = this.resolveVariableParameters(variableInfo.srcVariable.params,attribute.value.params);
+			$tw.utils.each(params,function(param,index) {
+				variables[param.name] = param.value;
+			});
+			var list = self.wiki.filterTiddlers(variableInfo.text,this.makeFakeWidgetWithVariables(variables));
+			value = list[0] || "";
+		} else {
+			value = variableInfo.text;
+		}
 	} else { // String attribute
 		value = attribute.value;
 	}
diff --git a/editions/test/tiddlers/tests/data/functions/FunctionAttributes.tid b/editions/test/tiddlers/tests/data/functions/FunctionAttributes.tid
new file mode 100644
index 000000000..2deb49bdc
--- /dev/null
+++ b/editions/test/tiddlers/tests/data/functions/FunctionAttributes.tid
@@ -0,0 +1,24 @@
+title: Functions/FunctionAttributes
+description: Attributes specified as function invocations
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+\whitespace trim
+\function .dividebysomething(factor:0.5)
+[divide<factor>]
+\end
+
+\function multiplebysomething(first:ignored,factor:2)
+[<factor>multiply[2].dividebysomething[0.25]]
+\end
+
+<$text text=<<multiplebysomething>>/>
+|
+<$text text=<<multiplebysomething "nothing" "4">>/>
+
++
+title: ExpectedResult
+
+<p>16|32</p>
\ No newline at end of file