diff --git a/src/vs/workbench/api/electron-browser/mainThreadDebugService.ts b/src/vs/workbench/api/electron-browser/mainThreadDebugService.ts
index 79ea63cecdd9a3954977f658f008c5a59798b06d..16908a6f7488a7c137f26520df0b59efed118d2b 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadDebugService.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadDebugService.ts
@@ -158,18 +158,18 @@ export class MainThreadDebugService implements MainThreadDebugServiceShape, IDeb
 		};
 		if (hasProvide) {
 			provider.provideDebugConfigurations = (folder) => {
-				return Promise.resolve(this._proxy.$provideDebugConfigurations(handle, folder));
+				return this._proxy.$provideDebugConfigurations(handle, folder);
 			};
 		}
 		if (hasResolve) {
 			provider.resolveDebugConfiguration = (folder, config) => {
-				return Promise.resolve(this._proxy.$resolveDebugConfiguration(handle, folder, config));
+				return this._proxy.$resolveDebugConfiguration(handle, folder, config);
 			};
 		}
 		if (hasProvideDebugAdapter) {
 			console.info('DebugConfigurationProvider.debugAdapterExecutable is deprecated and will be removed soon; please use DebugAdapterDescriptorFactory.createDebugAdapterDescriptor instead.');
 			provider.debugAdapterExecutable = (folder) => {
-				return Promise.resolve(this._proxy.$legacyDebugAdapterExecutable(handle, folder));
+				return this._proxy.$legacyDebugAdapterExecutable(handle, folder);
 			};
 		}
 		this._debugConfigurationProviders.set(handle, provider);
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index 5a875cb601978deeb4ef6e74e0d80cbebbc5ce73..54a9efe54d041335c2c4d1aa9f550432a7313e4f 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -1062,7 +1062,7 @@ export interface ExtHostDebugServiceShape {
 	$startDASession(handle: number, session: IDebugSessionDto): Promise<void>;
 	$stopDASession(handle: number): Promise<void>;
 	$sendDAMessage(handle: number, message: DebugProtocol.ProtocolMessage): void;
-	$resolveDebugConfiguration(handle: number, folder: UriComponents | undefined, debugConfiguration: IConfig): Promise<IConfig>;
+	$resolveDebugConfiguration(handle: number, folder: UriComponents | undefined, debugConfiguration: IConfig): Promise<IConfig | null | undefined>;
 	$provideDebugConfigurations(handle: number, folder: UriComponents | undefined): Promise<IConfig[]>;
 	$legacyDebugAdapterExecutable(handle: number, folderUri: UriComponents | undefined): Promise<IAdapterDescriptor>; // TODO@AW legacy
 	$provideDebugAdapter(handle: number, session: IDebugSessionDto): Promise<IAdapterDescriptor>;
diff --git a/src/vs/workbench/contrib/debug/common/debug.ts b/src/vs/workbench/contrib/debug/common/debug.ts
index 1fd99ba496087b25fd9268096cbbaa2441c0979c..1d81cefc146b67c5e8560a0e5e2cc31fee0f065f 100644
--- a/src/vs/workbench/contrib/debug/common/debug.ts
+++ b/src/vs/workbench/contrib/debug/common/debug.ts
@@ -542,7 +542,7 @@ export interface IDebuggerContribution extends IPlatformSpecificAdapterContribut
 
 export interface IDebugConfigurationProvider {
 	readonly type: string;
-	resolveDebugConfiguration?(folderUri: uri | undefined, debugConfiguration: IConfig): Promise<IConfig>;
+	resolveDebugConfiguration?(folderUri: uri | undefined, debugConfiguration: IConfig): Promise<IConfig | null | undefined>;
 	provideDebugConfigurations?(folderUri: uri | undefined): Promise<IConfig[]>;
 	debugAdapterExecutable?(folderUri: uri | undefined): Promise<IAdapterDescriptor>;		// TODO@AW legacy
 }
diff --git a/src/vs/workbench/contrib/debug/electron-browser/debugConfigurationManager.ts b/src/vs/workbench/contrib/debug/electron-browser/debugConfigurationManager.ts
index e6f01c26cdda67b7a9891da95da57b7575ce3231..2580f4e8aa003aa40db6f94478042c8c8fb03725 100644
--- a/src/vs/workbench/contrib/debug/electron-browser/debugConfigurationManager.ts
+++ b/src/vs/workbench/contrib/debug/electron-browser/debugConfigurationManager.ts
@@ -212,9 +212,9 @@ export class ConfigurationManager implements IConfigurationManager {
 		return providers.length > 0;
 	}
 
-	resolveConfigurationByProviders(folderUri: uri | undefined, type: string | undefined, debugConfiguration: IConfig): Promise<IConfig> {
+	resolveConfigurationByProviders(folderUri: uri | undefined, type: string | undefined, debugConfiguration: IConfig): Promise<IConfig | null | undefined> {
 		return this.activateDebuggers('onDebugResolve', type).then(() => {
-			// pipe the config through the promises sequentially. append at the end the '*' types
+			// pipe the config through the promises sequentially. Append at the end the '*' types
 			const providers = this.configProviders.filter(p => p.type === type && p.resolveDebugConfiguration)
 				.concat(this.configProviders.filter(p => p.type === '*' && p.resolveDebugConfiguration));
 
diff --git a/src/vs/workbench/contrib/debug/electron-browser/debugService.ts b/src/vs/workbench/contrib/debug/electron-browser/debugService.ts
index 1d95a644fe9592ab5cc2f24ced2feaacc45073b4..3a80893767c5e14e31e6fd557fdb175cc0697327 100644
--- a/src/vs/workbench/contrib/debug/electron-browser/debugService.ts
+++ b/src/vs/workbench/contrib/debug/electron-browser/debugService.ts
@@ -591,12 +591,20 @@ export class DebugService implements IDebugService {
 								}
 							}
 
-							let substitutionThenable: Promise<IConfig | undefined> = Promise.resolve(session.configuration);
+							let substitutionThenable: Promise<IConfig | null | undefined> = Promise.resolve(session.configuration);
 							if (launch && needsToSubstitute && unresolved) {
 								substitutionThenable = this.configurationManager.resolveConfigurationByProviders(launch.workspace ? launch.workspace.uri : undefined, unresolved.type, unresolved)
-									.then(resolved => this.substituteVariables(launch, resolved));
+									.then(resolved => {
+										if (resolved) {
+											return this.substituteVariables(launch, resolved);
+										} else {
+											// resolve is null or undefined here
+											return Promise.resolve(resolved);
+										}
+									});
 							}
 							substitutionThenable.then(resolved => {
+
 								if (!resolved) {
 									return c(undefined);
 								}