diff --git a/src/vs/workbench/api/browser/mainThreadDebugService.ts b/src/vs/workbench/api/browser/mainThreadDebugService.ts
index 4e48c4bf864..9686820a36a 100644
--- a/src/vs/workbench/api/browser/mainThreadDebugService.ts
+++ b/src/vs/workbench/api/browser/mainThreadDebugService.ts
@@ -75,7 +75,7 @@ export class MainThreadDebugService implements MainThreadDebugServiceShape, IDeb
 	}
 
 	runInTerminal(args: DebugProtocol.RunInTerminalRequestArguments): Promise<number | undefined> {
-		return Promise.resolve(this._proxy.$runInTerminal(args));
+		return this._proxy.$runInTerminal(args);
 	}
 
 	// RPC methods (MainThreadDebugServiceShape)
diff --git a/src/vs/workbench/api/node/extHostDebugService.ts b/src/vs/workbench/api/node/extHostDebugService.ts
index dab72ef96b4..23ec3e88954 100644
--- a/src/vs/workbench/api/node/extHostDebugService.ts
+++ b/src/vs/workbench/api/node/extHostDebugService.ts
@@ -113,7 +113,7 @@ export class ExtHostDebugService extends ExtHostDebugServiceBase {
 
 		} else if (args.kind === 'external') {
 
-			runInExternalTerminal(args, await this._configurationService.getConfigProvider());
+			return runInExternalTerminal(args, await this._configurationService.getConfigProvider());
 		}
 		return super.$runInTerminal(args);
 	}
diff --git a/src/vs/workbench/contrib/debug/node/terminals.ts b/src/vs/workbench/contrib/debug/node/terminals.ts
index 6be7695e38f..89e850f23aa 100644
--- a/src/vs/workbench/contrib/debug/node/terminals.ts
+++ b/src/vs/workbench/contrib/debug/node/terminals.ts
@@ -12,7 +12,7 @@ import { ExtHostConfigProvider } from 'vs/workbench/api/common/extHostConfigurat
 
 let externalTerminalService: IExternalTerminalService | undefined = undefined;
 
-export function runInExternalTerminal(args: DebugProtocol.RunInTerminalRequestArguments, configProvider: ExtHostConfigProvider): void {
+export function runInExternalTerminal(args: DebugProtocol.RunInTerminalRequestArguments, configProvider: ExtHostConfigProvider): Promise<number | undefined> {
 	if (!externalTerminalService) {
 		if (env.isWindows) {
 			externalTerminalService = new WindowsExternalTerminalService(<IConfigurationService><unknown>undefined);
@@ -20,12 +20,12 @@ export function runInExternalTerminal(args: DebugProtocol.RunInTerminalRequestAr
 			externalTerminalService = new MacExternalTerminalService(<IConfigurationService><unknown>undefined);
 		} else if (env.isLinux) {
 			externalTerminalService = new LinuxExternalTerminalService(<IConfigurationService><unknown>undefined);
+		} else {
+			throw new Error('external terminals not supported on this platform');
 		}
 	}
-	if (externalTerminalService) {
-		const config = configProvider.getConfiguration('terminal');
-		externalTerminalService.runInTerminal(args.title!, args.cwd, args.args, args.env || {}, config.external || {});
-	}
+	const config = configProvider.getConfiguration('terminal');
+	return externalTerminalService.runInTerminal(args.title!, args.cwd, args.args, args.env || {}, config.external || {});
 }
 
 function spawnAsPromised(command: string, args: string[]): Promise<string> {