diff --git a/core/modules/parsers/wikiparser/rules/fnprocdef.js b/core/modules/parsers/wikiparser/rules/fnprocdef.js
index 0f6618292..12ac33cac 100644
--- a/core/modules/parsers/wikiparser/rules/fnprocdef.js
+++ b/core/modules/parsers/wikiparser/rules/fnprocdef.js
@@ -35,7 +35,7 @@ Instantiate parse rule
 exports.init = function(parser) {
 	this.parser = parser;
 	// Regexp to match
-	this.matchRegExp = /^\\(function|procedure|widget)\s+([^(\s]+)(\(\s*([^)]*)\))?(\s*\r?\n)?/mg;
+	this.matchRegExp = /^\\(function|procedure|widget)\s+([^(\s]+)\((\s*([^)]*))?\)(\s*\r?\n)?/mg;
 };
 
 /*
diff --git a/editions/test/tiddlers/tests/data/genesis-widget/RedefineLet.tid b/editions/test/tiddlers/tests/data/genesis-widget/RedefineLet.tid
index 184f6014f..f6834998d 100644
--- a/editions/test/tiddlers/tests/data/genesis-widget/RedefineLet.tid
+++ b/editions/test/tiddlers/tests/data/genesis-widget/RedefineLet.tid
@@ -6,7 +6,7 @@ tags: [[$:/tags/wiki-test-spec]]
 title: Output
 
 \whitespace trim
-\widget $let
+\widget $let()
 \whitespace trim
 <$parameters $params="@params">
 <$setmultiplevariables $names="[<@params>jsonindexes[]]" $values="[<@params>jsonindexes[]] :map[<@params>jsonget<currentTiddler>addprefix[--]addsuffix[--]]">
diff --git a/editions/test/tiddlers/tests/test-wikitext-parser.js b/editions/test/tiddlers/tests/test-wikitext-parser.js
index 18486f7c2..bc3d9acd8 100644
--- a/editions/test/tiddlers/tests/test-wikitext-parser.js
+++ b/editions/test/tiddlers/tests/test-wikitext-parser.js
@@ -121,7 +121,7 @@ describe("WikiText parser tests", function() {
 	});
 
 	it("should parse procedure definitions with no parameters", function() {
-		expect(parse("\\procedure myMacro\nnothing\n\\end\n")).toEqual(
+		expect(parse("\\procedure myMacro()\nnothing\n\\end\n")).toEqual(
 
 			[{"type":"set","attributes":{"name":{"name":"name","type":"string","value":"myMacro"},"value":{"name":"value","type":"string","value":"nothing"}},"children":[],"params":[],"orderedAttributes":[{"name":"name","type":"string","value":"myMacro"},{"name":"value","type":"string","value":"nothing"}],"isProcedureDefinition":true}]
 
@@ -129,7 +129,7 @@ describe("WikiText parser tests", function() {
 	});
 
 	it("should parse single line procedure definitions with no parameters", function() {
-		expect(parse("\\procedure myMacro nothing\n")).toEqual(
+		expect(parse("\\procedure myMacro() nothing\n")).toEqual(
 
 			[{"type":"set","attributes":{"name":{"name":"name","type":"string","value":"myMacro"},"value":{"name":"value","type":"string","value":"nothing"}},"children":[],"params":[],"orderedAttributes":[{"name":"name","type":"string","value":"myMacro"},{"name":"value","type":"string","value":"nothing"}],"isProcedureDefinition":true}]
 
@@ -152,7 +152,7 @@ describe("WikiText parser tests", function() {
 		);
 
 	});	it("should parse function definitions with no parameters", function() {
-		expect(parse("\\function myMacro\nnothing\n\\end\n")).toEqual(
+		expect(parse("\\function myMacro()\nnothing\n\\end\n")).toEqual(
 
 			[{"type":"set","attributes":{"name":{"name":"name","type":"string","value":"myMacro"},"value":{"name":"value","type":"string","value":"nothing"}},"children":[],"params":[],"orderedAttributes":[{"name":"name","type":"string","value":"myMacro"},{"name":"value","type":"string","value":"nothing"}],"isFunctionDefinition":true}]
 
@@ -160,7 +160,7 @@ describe("WikiText parser tests", function() {
 	});
 
 	it("should parse single line function definitions with no parameters", function() {
-		expect(parse("\\function myMacro nothing\n")).toEqual(
+		expect(parse("\\function myMacro() nothing\n")).toEqual(
 
 			[{"type":"set","attributes":{"name":{"name":"name","type":"string","value":"myMacro"},"value":{"name":"value","type":"string","value":"nothing"}},"children":[],"params":[],"orderedAttributes":[{"name":"name","type":"string","value":"myMacro"},{"name":"value","type":"string","value":"nothing"}],"isFunctionDefinition":true}]