diff --git a/src/classes/site.ts b/src/classes/site.ts
index 553a1cf19..261887d74 100644
--- a/src/classes/site.ts
+++ b/src/classes/site.ts
@@ -482,14 +482,7 @@ export class CoreSite {
 
                 // We pass back a clone of the original object, this may
                 // prevent errors if in the callback the object is modified.
-                if (typeof response == 'object') {
-                    if (Array.isArray(response)) {
-                        return Array.from(response);
-                    } else {
-                        return Object.assign({}, response);
-                    }
-                }
-                return response;
+                return this.utils.clone(response);
             }).catch((error) => {
                 if (error.errorcode == 'invalidtoken' ||
                         (error.errorcode == 'accessexception' && error.message.indexOf('Invalid token - token expired') > -1)) {
diff --git a/src/providers/utils/utils.ts b/src/providers/utils/utils.ts
index 6283863e8..c2a084f09 100644
--- a/src/providers/utils/utils.ts
+++ b/src/providers/utils/utils.ts
@@ -307,15 +307,14 @@ export class CoreUtilsProvider {
      *
      * @param {any} from Object to copy the properties from.
      * @param {any} to Object where to store the properties.
+     * @param {boolean} [clone=true] Whether the properties should be cloned (so they are different instances).
      */
-    copyProperties(from: any, to: any) : void {
+    copyProperties(from: any, to: any, clone = true) : void {
         for (let name in from) {
-            let value = from[name];
-            if (typeof value == 'object') {
-                // Clone the object.
-                to[name] = Object.assign({}, value);
+            if (clone) {
+                to[name] = this.clone(from[name]);
             } else {
-                to[name] = value;
+                to[name] = from[name];
             }
         }
     }
@@ -413,15 +412,16 @@ export class CoreUtilsProvider {
         for (let name in obj) {
             if (!obj.hasOwnProperty(name)) continue;
 
-            if (typeof obj[name] == 'object') {
-                let flatObject = this.flattenObject(obj[name]);
+            let value = obj[name];
+            if (typeof value == 'object' && !Array.isArray(value)) {
+                let flatObject = this.flattenObject(value);
                 for (let subName in flatObject) {
                     if (!flatObject.hasOwnProperty(subName)) continue;
 
                     toReturn[name + '.' + subName] = flatObject[subName];
                 }
             } else {
-                toReturn[name] = obj[name];
+                toReturn[name] = value;
             }
         }
 
@@ -1109,7 +1109,26 @@ export class CoreUtilsProvider {
      * @return {string} Stringified object.
      */
     sortAndStringify(obj: object) : string {
-        return JSON.stringify(obj, Object.keys(this.flattenObject(obj)).sort());
+        return JSON.stringify(this.sortProperties(obj));
+    }
+
+    /**
+     * Given an object, sort its properties and the properties of all the nested objects.
+     *
+     * @param {object} obj The object to sort. If it isn't an object, the original value will be returned.
+     * @return {object} Sorted object.
+     */
+    sortProperties(obj: object) : object {
+        if (typeof obj == 'object' && !Array.isArray(obj)) {
+            // It's an object, sort it.
+            return Object.keys(obj).sort().reduce((accumulator, key) => {
+                // Always call sort with the value. If it isn't an object, the original value will be returned.
+                accumulator[key] = this.sortProperties(obj[key]);
+                return accumulator;
+            }, {});
+        } else {
+            return obj;
+        }
     }
 
     /**
diff --git a/src/providers/ws.ts b/src/providers/ws.ts
index d5fb825f4..02d04fba4 100644
--- a/src/providers/ws.ts
+++ b/src/providers/ws.ts
@@ -126,6 +126,8 @@ export class CoreWSProvider {
             preSets.responseExpected = true;
         }
 
+        data = data || {};
+        data = this.utils.clone(data); // Clone the data so the changes don't affect the original data.
         data.wsfunction = method;
         data.wstoken = preSets.wsToken;
         siteUrl = preSets.siteUrl + '/webservice/rest/server.php?moodlewsrestformat=json';