diff --git a/src/putility/src/concepts/Service.js b/src/putility/src/concepts/Service.js
index 57b0ba46..30668d36 100644
--- a/src/putility/src/concepts/Service.js
+++ b/src/putility/src/concepts/Service.js
@@ -2,6 +2,9 @@ const { AdvancedBase } = require("../AdvancedBase");
 
 const NOOP = async () => {};
 
+/** Service trait */
+const TService = Symbol('TService');
+
 /**
  * Service will be incrementally updated to consolidate
  * BaseService in Puter's backend with Service in Puter's frontend,
@@ -23,23 +26,27 @@ class Service extends AdvancedBase {
     static create ({ parameters, context }) {
         const ins = new this();
         ins._.context = context;
-        ins.construct(parameters);
+        ins.as(TService).construct(parameters);
         return ins;
     }
 
-    init (...a) {
-        if ( ! this._init ) return;
-        return this._init(...a);
-    }
-
-    construct (o) {
-        this.$parameters = {};
-        for ( const k in o ) this.$parameters[k] = o[k];
-        if ( ! this._construct ) return;
-        return this._construct(o);
+    static IMPLEMENTS = {
+        [TService]: {
+            init (...a) {
+                if ( ! this._init ) return;
+                return this._init(...a);
+            },
+            construct (o) {
+                this.$parameters = {};
+                for ( const k in o ) this.$parameters[k] = o[k];
+                if ( ! this._construct ) return;
+                return this._construct(o);
+            }
+        }
     }
 }
 
 module.exports = {
+    TService,
     Service,
 };
diff --git a/src/putility/src/features/PropertiesFeature.js b/src/putility/src/features/PropertiesFeature.js
index 90a9572b..b5ec2b22 100644
--- a/src/putility/src/features/PropertiesFeature.js
+++ b/src/putility/src/features/PropertiesFeature.js
@@ -18,14 +18,15 @@
  */
 module.exports = {
     name: 'Properties',
+    depends: ['Listeners'],
     install_in_instance: (instance) => {
         const properties = instance._get_merged_static_object('PROPERTIES');
 
         instance.onchange = (name, callback) => {
-            instance.__properties[name].listeners.push(callback);
+            instance._.properties[name].listeners.push(callback);
         };
 
-        instance.__properties = {};
+        instance._.properties = {};
 
         for ( const k in properties ) {
             const state = {
@@ -33,7 +34,7 @@ module.exports = {
                 listeners: [],
                 value: undefined,
             };
-            instance.__properties[k] = state;
+            instance._.properties[k] = state;
 
             if ( typeof properties[k] === 'object' ) {
                 // This will be supported in the future.
@@ -54,7 +55,7 @@ module.exports = {
                     return state.value;
                 },
                 set: (value) => {
-                    for ( const listener of instance.__properties[k].listeners ) {
+                    for ( const listener of instance._.properties[k].listeners ) {
                         listener(value, {
                             old_value: instance[k],
                         });
diff --git a/src/putility/src/features/TraitsFeature.js b/src/putility/src/features/TraitsFeature.js
index 2da996b7..ba597251 100644
--- a/src/putility/src/features/TraitsFeature.js
+++ b/src/putility/src/features/TraitsFeature.js
@@ -30,7 +30,11 @@ module.exports = {
         for ( const cls of chain ) {
             const cls_traits = cls.IMPLEMENTS;
             if ( ! cls_traits ) continue;
-            for ( const trait_name in cls_traits ) {
+            const trait_keys = [
+                ...Object.getOwnPropertySymbols(cls_traits),
+                ...Object.keys(cls_traits),
+            ];
+            for ( const trait_name of trait_keys ) {
                 const impl = instance._.impls[trait_name] ??
                     (instance._.impls[trait_name] = {});
                 const cls_impl = cls_traits[trait_name];
diff --git a/src/putility/src/system/ServiceManager.js b/src/putility/src/system/ServiceManager.js
index 95c5cbbc..a2e67987 100644
--- a/src/putility/src/system/ServiceManager.js
+++ b/src/putility/src/system/ServiceManager.js
@@ -1,4 +1,5 @@
 const { AdvancedBase } = require("../AdvancedBase");
+const { TService } = require("../concepts/Service");
 
 const mkstatus = name => {
     const c = class {
@@ -99,7 +100,9 @@ class ServiceManager extends AdvancedBase {
     async init_service_ (name) {
         const entry = this.services_m_[name];
         entry.status = new this.constructor.StatusInitializing();
-        await entry.instance.init();
+
+        const service_impl = entry.instance.as(TService);
+        await service_impl.init();
         entry.status = new this.constructor.StatusRunning({
             start_ts: new Date(),
         });