diff --git a/src/session_nub.ts b/src/session_nub.ts
index a8ce1687412c6b4823fde17eb9dec524de40dcf4..00773aa804be63fe6afcd17de4cc328535e20332 100644
--- a/src/session_nub.ts
+++ b/src/session_nub.ts
@@ -74,7 +74,9 @@ export class Props implements IObservable {
     public clone(): Props {
         const res = new Props();
         for (const k in this._props) {
-            res._props[k] = this._props[k];
+            if (this._props.hasOwnProperty(k)) {
+                res._props[k] = this._props[k];
+            }
         }
         return res;
     }
@@ -82,12 +84,14 @@ export class Props implements IObservable {
     public toString(): string {
         let res = "[";
         for (const k in this._props) {
-            if (res !== "[") {
-                res += ", ";
+            if (this._props.hasOwnProperty(k)) {
+                if (res !== "[") {
+                    res += ", ";
+                }
+                res += `${k}:${this._props[k]}`;
             }
-            res += `${k}:${this._props[k]}`;
         }
-        res += "]"
+        res += "]";
         return res;
     }
 
@@ -174,6 +178,7 @@ export class Props implements IObservable {
 /**
  * Nub utilisé dans une session
  */
+// tslint:disable-next-line:max-classes-per-file
 export class SessionNub {
     private _props: Props;