diff --git a/dev/Sieve/Commands.js b/dev/Sieve/Commands.js
index 941b4e409..e2c59e5fa 100644
--- a/dev/Sieve/Commands.js
+++ b/dev/Sieve/Commands.js
@@ -48,6 +48,7 @@ import { NotifyCommand, ValidNotifyMethodTest, NotifyMethodCapabilityTest } from
 import { IHaveTest, ErrorCommand } from 'Sieve/Extensions/rfc5463';
 import { MailboxExistsTest, MetadataTest, MetadataExistsTest } from 'Sieve/Extensions/rfc5490';
 import { ForEveryPartCommand, BreakCommand, ReplaceCommand, EncloseCommand, ExtractTextCommand } from 'Sieve/Extensions/rfc5703';
+import { ValidExtListTest } from 'Sieve/Extensions/rfc6134';
 import { IncludeCommand, ReturnCommand, GlobalCommand } from 'Sieve/Extensions/rfc6609';
 
 export const
@@ -127,6 +128,8 @@ export const
 		ReplaceCommand,
 		EncloseCommand,
 		ExtractTextCommand,
+		// rfc6134
+		ValidExtListTest,
 		// rfc6609
 		IncludeCommand,
 		ReturnCommand,
@@ -144,6 +147,17 @@ export const
 		return commands;
 	},
 
+	unavailableCommands = () => {
+		let commands = {};
+		AllCommands.forEach(cmd => {
+			const obj = new cmd, requires = obj.require;
+			if (requires && !(Array.isArray(requires) ? requires : [requires]).every(string => capa.includes(string))) {
+				commands[obj.identifier] = cmd;
+			}
+		});
+		return commands;
+	},
+
 	availableActions = () => {
 		let actions = {}, id;
 		AllCommands.forEach(cmd => {
diff --git a/dev/Sieve/Extensions/rfc5230.js b/dev/Sieve/Extensions/rfc5230.js
index e1a552c32..a5937a3bd 100644
--- a/dev/Sieve/Extensions/rfc5230.js
+++ b/dev/Sieve/Extensions/rfc5230.js
@@ -80,7 +80,8 @@ export class VacationCommand extends ActionCommand
 				this.addresses = arg; // GrammarStringList
 			} else if (i && ':' === args[i-1][0]) {
 				// :days, :seconds, :subject, :from, :handle
-				this[args[i-1].replace(':','_')].value = arg.value;
+				let p = args[i-1].replace(':','_');
+				this[p] ? (this[p].value = arg.value) : console.log('Unknown VacationCommand :' + p);
 			}
 		});
 	}
diff --git a/dev/Sieve/Extensions/rfc5235.js b/dev/Sieve/Extensions/rfc5235.js
index bfec1bb57..1c8bc46b2 100644
--- a/dev/Sieve/Extensions/rfc5235.js
+++ b/dev/Sieve/Extensions/rfc5235.js
@@ -51,7 +51,7 @@ export class VirusTestTest extends TestCommand
 		this._value = new GrammarQuotedString; // 1 - 5
 	}
 
-	get require() { return /:value|:count/.test(this.match_type) ? ['virustest','relational'] : 'virustest'; }
+	get require() { return /:value/.test(this.match_type) ? ['virustest','relational'] : 'virustest'; }
 
 	get value() { return this._value.value; }
 	set value(v) { this._value.value = v; }
diff --git a/dev/Sieve/Extensions/rfc5435.js b/dev/Sieve/Extensions/rfc5435.js
index 3595ee502..9bee9fdb6 100644
--- a/dev/Sieve/Extensions/rfc5435.js
+++ b/dev/Sieve/Extensions/rfc5435.js
@@ -65,7 +65,8 @@ export class NotifyCommand extends ActionCommand
 				this.options = arg; // GrammarStringList
 			} else if (i && ':' === args[i-1][0]) {
 				// :from, :importance, :message
-				this[args[i-1].replace(':','_')].value = arg.value;
+				let p = args[i-1].replace(':','_');
+				this[p] ? (this[p].value = arg.value) : console.log('Unknown VacationCommand :' + p);
 			}
 		});
 	}
diff --git a/dev/Sieve/Extensions/rfc5703.js b/dev/Sieve/Extensions/rfc5703.js
index 46302018d..552e04c2f 100644
--- a/dev/Sieve/Extensions/rfc5703.js
+++ b/dev/Sieve/Extensions/rfc5703.js
@@ -108,7 +108,8 @@ export class ReplaceCommand extends ActionCommand
 				this.mime = true;
 			} else if (i && ':' === args[i-1][0]) {
 				// :subject, :from
-				this[args[i-1].replace(':','_')].value = arg.value;
+				let p = args[i-1].replace(':','_');
+				this[p] ? (this[p].value = arg.value) : console.log('Unknown VacationCommand :' + p);
 			}
 		});
 	}
@@ -148,7 +149,8 @@ export class EncloseCommand extends ActionCommand
 		args.forEach((arg, i) => {
 			if (i && ':' === args[i-1][0]) {
 				// :subject, :headers
-				this[args[i-1].replace(':','_')].value = arg.value;
+				let p = args[i-1].replace(':','_');
+				this[p] ? (this[p].value = arg.value) : console.log('Unknown VacationCommand :' + p);
 			}
 		});
 	}
diff --git a/dev/Sieve/Extensions/rfc6134.js b/dev/Sieve/Extensions/rfc6134.js
index 872938eab..1bdb7c8b0 100644
--- a/dev/Sieve/Extensions/rfc6134.js
+++ b/dev/Sieve/Extensions/rfc6134.js
@@ -14,7 +14,7 @@ export class ValidExtListTest extends TestCommand
 {
 	constructor()
 	{
-		super();
+		super('valid_ext_list');
 		this.ext_list_names = new GrammarStringList;
 	}
 
diff --git a/dev/Sieve/Parser.js b/dev/Sieve/Parser.js
index 64364cf95..8ef1dacc3 100644
--- a/dev/Sieve/Parser.js
+++ b/dev/Sieve/Parser.js
@@ -28,7 +28,7 @@ import {
 	GrammarTestList
 } from 'Sieve/Grammar';
 
-import { availableCommands } from 'Sieve/Commands';
+import { availableCommands, unavailableCommands } from 'Sieve/Commands';
 import { ConditionalCommand, IfCommand, RequireCommand } from 'Sieve/Commands/Controls';
 import { NotTest } from 'Sieve/Commands/Tests';
 
@@ -93,6 +93,7 @@ export const parseScript = (script, name = 'script.sieve') => {
 
 	// Only activate available commands
 	const Commands = availableCommands();
+	const disabledCommands = unavailableCommands();
 
 	let match,
 		line = 1,
@@ -173,17 +174,12 @@ export const parseScript = (script, name = 'script.sieve') => {
 //					(command instanceof ConditionalCommand || command instanceof NotTest) || error('Test-list not in conditional');
 				}
 				new_command = new Commands[value]();
+			} else if (disabledCommands[value]) {
+				console.error('Unsupported command: ' + value);
+				new_command = new disabledCommands[value]();
 			} else {
-				if (command && (
-				    command instanceof ConditionalCommand
-				 || command instanceof NotTest
-				 || command.tests instanceof GrammarTestList)) {
-					console.error('Unknown test: ' + value);
-					new_command = new TestCommand(value);
-				} else {
-					console.error('Unknown command: ' + value);
-					new_command = new GrammarCommand(value);
-				}
+				console.error('Unknown command: ' + value);
+				new_command = new GrammarCommand(value);
 			}
 
 			if (new_command instanceof TestCommand) {
@@ -201,7 +197,7 @@ export const parseScript = (script, name = 'script.sieve') => {
 				if (command.commands) {
 					command.commands.push(new_command);
 				} else {
-					error('commands not allowed in "' + command.identifier + '" command');
+					error('command "' + new_command.identifier + '" not allowed in "' + command.identifier + '" command');
 				}
 			} else {
 				tree.push(new_command);