diff --git a/src/vs/base/common/marshalling.ts b/src/vs/base/common/marshalling.ts
index 7536ec5210dd1cfaa34d55f43c799c1fcc6d4092..9275b413307c6746eb527f7f7376caad4085b355 100644
--- a/src/vs/base/common/marshalling.ts
+++ b/src/vs/base/common/marshalling.ts
@@ -30,9 +30,6 @@ function replacer(key: string, value: any): any {
 	return value;
 }
 
-// TODO@Joao hack?
-export const ResolverRegistry: { [mid: number]: (value: any) => any; } = Object.create(null);
-
 function reviver(key: string, value: any): any {
 	let marshallingConst: number;
 	if (value !== void 0 && value !== null) {
@@ -42,13 +39,6 @@ function reviver(key: string, value: any): any {
 	switch (marshallingConst) {
 		case 1: return URI.revive(value);
 		case 2: return new RegExp(value.source, value.flags);
-		default:
-			const resolver = ResolverRegistry[marshallingConst];
-
-			if (resolver) {
-				return resolver(value);
-			} else {
-				return value;
-			}
+		default: return value;
 	}
 }
diff --git a/src/vs/workbench/api/node/extHostCommands.ts b/src/vs/workbench/api/node/extHostCommands.ts
index e8ebf85b36fdd120ba19d6483643a50398d52f88..6f99ac35fe8b23809ab8e53b38c499929b253fb3 100644
--- a/src/vs/workbench/api/node/extHostCommands.ts
+++ b/src/vs/workbench/api/node/extHostCommands.ts
@@ -23,11 +23,16 @@ interface CommandHandler {
 	description: ICommandHandlerDescription;
 }
 
+export interface ArgumentProcessor {
+	processArgument(arg: any): any;
+}
+
 export class ExtHostCommands extends ExtHostCommandsShape {
 
 	private _commands = new Map<string, CommandHandler>();
 	private _proxy: MainThreadCommandsShape;
 	private _converter: CommandsConverter;
+	private _argumentProcessors: ArgumentProcessor[] = [];
 
 	constructor(
 		threadService: IThreadService,
@@ -42,6 +47,10 @@ export class ExtHostCommands extends ExtHostCommandsShape {
 		return this._converter;
 	}
 
+	registerArgumentProcessor(processor: ArgumentProcessor): void {
+		this._argumentProcessors.push(processor);
+	}
+
 	registerCommand(id: string, callback: <T>(...args: any[]) => T | Thenable<T>, thisArg?: any, description?: ICommandHandlerDescription): extHostTypes.Disposable {
 
 		if (!id.trim().length) {
@@ -110,6 +119,8 @@ export class ExtHostCommands extends ExtHostCommandsShape {
 			}
 		}
 
+		args = args.map(arg => this._argumentProcessors.reduce((r, p) => p.processArgument(r), arg));
+
 		try {
 			let result = callback.apply(thisArg, args);
 			return TPromise.as(result);
diff --git a/src/vs/workbench/api/node/extHostSCM.ts b/src/vs/workbench/api/node/extHostSCM.ts
index 92f855c0f65577600eb0f9a63b8945f53369a59e..84b6e8c8ef94eba0a66806ce50c6cee1d24b0367 100644
--- a/src/vs/workbench/api/node/extHostSCM.ts
+++ b/src/vs/workbench/api/node/extHostSCM.ts
@@ -12,7 +12,6 @@ import { IThreadService } from 'vs/workbench/services/thread/common/threadServic
 import { ExtHostCommands, CommandsConverter } from 'vs/workbench/api/node/extHostCommands';
 import { MainContext, MainThreadSCMShape, SCMRawResource } from './extHost.protocol';
 import * as vscode from 'vscode';
-import * as marshalling from 'vs/base/common/marshalling';
 
 function getIconPath(decorations: vscode.SourceControlResourceThemableDecorations) {
 	if (!decorations) {
@@ -241,16 +240,21 @@ export class ExtHostSCM {
 		this._proxy = threadService.get(MainContext.MainThreadSCM);
 		this._inputBox = new ExtHostSCMInputBox(this._proxy);
 
-		// TODO@joao HACK
-		marshalling.ResolverRegistry[3] = value => {
-			const sourceControl = this._sourceControls.get(value.sourceControlHandle);
+		_commands.registerArgumentProcessor({
+			processArgument: arg => {
+				if (arg && arg.$mid === 3) {
+					const sourceControl = this._sourceControls.get(arg.sourceControlHandle);
 
-			if (!sourceControl) {
-				return value;
-			}
+					if (!sourceControl) {
+						return arg;
+					}
+
+					return sourceControl.getResourceState(arg.groupHandle, arg.handle);
+				}
 
-			return sourceControl.getResourceState(value.groupHandle, value.handle);
-		};
+				return arg;
+			}
+		});
 	}
 
 	createSourceControl(id: string, label: string): vscode.SourceControl {