diff --git a/src/main/ts/di/Container.ts b/src/main/ts/di/Container.ts
--- a/src/main/ts/di/Container.ts
+++ b/src/main/ts/di/Container.ts
@@ -50,11 +50,13 @@ export class Container<S extends object 
         return this._lifetimeManager;
     }
 
-    resolve<K extends ContainerKeys<S>>(name: K, def?: TypeOfService<S, K>): TypeOfService<S, K> {
+    resolve<K extends ContainerKeys<S>>(name: K, def?: TypeOfService<S, K>): TypeOfService<S, K>;
+    resolve<K extends ContainerKeys<S>>(name: K, def: undefined): TypeOfService<S, K> | undefined;
+    resolve<K extends ContainerKeys<S>>(name: K, def?: TypeOfService<S, K>): TypeOfService<S, K> | undefined {
         trace.debug("resolve {0}", name);
         const d = this._services[name];
         if (d === undefined) {
-            if (def !== undefined)
+            if (arguments.length > 1)
                 return def;
             else
                 throw new Error("Service '" + name + "' isn't found");
@@ -73,7 +75,7 @@ export class Container<S extends object 
      * @deprecated use resolve() method
      */
     getService<K extends ContainerKeys<S>>(name: K, def?: TypeOfService<S, K>) {
-        return this.resolve(name, def);
+        return arguments.length === 1 ? this.resolve(name) : this.resolve(name, def);
     }
 
     register<K extends keyof S>(name: K, service: Descriptor<S, S[K]>): this;
@@ -108,6 +110,7 @@ export class Container<S extends object 
         this._disposed = true;
         for (const f of this._cleanup)
             f();
+        this._lifetimeManager.destroy();
     }
 
     /**
diff --git a/src/main/ts/di/LifetimeManager.ts b/src/main/ts/di/LifetimeManager.ts
--- a/src/main/ts/di/LifetimeManager.ts
+++ b/src/main/ts/di/LifetimeManager.ts
@@ -1,5 +1,5 @@
 import { IDestroyable, MapOf } from "../interfaces";
-import { argumentNotNull, isDestroyable, argumentNotEmptyString } from "../safe";
+import { argumentNotNull, isDestroyable, argumentNotEmptyString, isRemovable } from "../safe";
 import { ILifetime, ServiceContainer } from "./interfaces";
 import { ActivationContext } from "./ActivationContext";
 
@@ -93,6 +93,8 @@ export class LifetimeManager implements 
                     self._cleanup.push(() => cleanup(item));
                 } else if (isDestroyable(item)) {
                     self._cleanup.push(() => item.destroy());
+                } else if (isRemovable(item)) {
+                    self._cleanup.push(() => item.remove());
                 }
             }
         };
diff --git a/src/main/ts/di/interfaces.ts b/src/main/ts/di/interfaces.ts
--- a/src/main/ts/di/interfaces.ts
+++ b/src/main/ts/di/interfaces.ts
@@ -26,6 +26,7 @@ export type PartialServiceMap<S extends 
 
 export interface ServiceLocator<S extends object> {
     resolve<K extends ContainerKeys<S>>(name: K, def?: TypeOfService<S, K>): TypeOfService<S, K>;
+    resolve<K extends ContainerKeys<S>>(name: K, def?: undefined): TypeOfService<S, K> | undefined;
 }
 
 export interface ServiceContainer<S extends object> extends ServiceLocator<S>, IDestroyable {
diff --git a/src/main/ts/safe.ts b/src/main/ts/safe.ts
--- a/src/main/ts/safe.ts
+++ b/src/main/ts/safe.ts
@@ -1,4 +1,4 @@
-import { ICancellable, Constructor, IDestroyable, ICancellation } from "./interfaces";
+import { ICancellable, Constructor, IDestroyable, ICancellation, IRemovable } from "./interfaces";
 
 let _nextOid = 0;
 const _oid = typeof Symbol === "function" ?
@@ -62,10 +62,6 @@ export function argumentOfType(arg: any,
         throw new Error("The argument '" + name + "' type doesn't match");
 }
 
-export function isObject(val: any): val is object {
-    return typeof val === "object";
-}
-
 export function isNull(val: any): val is null | undefined {
     return (val === null || val === undefined);
 }
@@ -77,6 +73,10 @@ export function isPrimitive(val: any): v
         typeof (val) === "number" || typeof (val) === "boolean");
 }
 
+export function isObject<T>(value: T): value is Exclude<T & object, primitive> {
+    return !!(value && typeof value === "object");
+}
+
 export function isInteger(val: any): val is number {
     return parseInt(val, 10) === val;
 }
@@ -86,15 +86,15 @@ export function isNumber(val: any): val 
 }
 
 export function isString(val: any): val is string {
-    return typeof (val) === "string" || val instanceof String;
+    return typeof (val) === "string";
 }
 
 export function isPromise<T = any>(val: any): val is PromiseLike<T> {
-    return val && typeof val.then === "function";
+    return !!(val && typeof val.then === "function");
 }
 
 export function isCancellable(val: any): val is ICancellable {
-    return val && typeof val.cancel === "function";
+    return !!(val && typeof val.cancel === "function");
 }
 
 export function isNullOrEmptyString(val: any): val is ("" | null | undefined) {
@@ -315,7 +315,7 @@ export function fork() {
  * assigned later and are required to be not null.
  */
 export function notImplemented(): never {
-    throw new Error("Not implemeted");
+    throw new Error("Not implemented");
 }
 /**
  * Iterates over the specified array of items and calls the callback `cb`, if
@@ -491,13 +491,15 @@ export function firstWhere<T>(
 }
 
 export function isDestroyable(d: any): d is IDestroyable {
-    if (d && "destroy" in d && typeof (destroy) === "function")
-        return true;
-    return false;
+    return !!(d && typeof d.destroy === "function");
+}
+
+export function isRemovable(value: any): value is IRemovable {
+    return !!(value && typeof value.remove === "function");
 }
 
 export function destroy(d: any) {
-    if (d && "destroy" in d)
+    if (isDestroyable(d))
         d.destroy();
 }
 
diff --git a/src/tsconfig.json b/src/tsconfig.json
--- a/src/tsconfig.json
+++ b/src/tsconfig.json
@@ -4,7 +4,7 @@
         "experimentalDecorators": true,
         "noEmitOnError": true,
         "listFiles": true,
-        //"strict": true,
+        "strict": true,
         "types": [],
         "target": "ES5",
         "lib": ["es5", "es2015.promise", "es2015.symbol", "es2015.iterable", "dom", "scripthost"]