diff --git a/testing/marionette/marionette-server.js b/testing/marionette/marionette-server.js
index ee58a90fd78..621ae09b6d6 100644
--- a/testing/marionette/marionette-server.js
+++ b/testing/marionette/marionette-server.js
@@ -1621,6 +1621,26 @@ MarionetteServerConnection.prototype = {
     }
   },
 
+  /**
+   * Find element using the indicated search strategy
+   * starting from a known element. Used for WebDriver Compatibility only.
+   * @param  {object} aRequest
+   *         'using' member indicates which search method to use
+   *         'value' member is the value the client is looking for
+   *         'id' member is the value of the element to start from
+   */
+  findChildElement: function MDA_findChildElement(aRequest) {
+    let command_id = this.command_id = this.getCommandId();
+    this.sendAsync("findElementContent",
+                    {
+                       value: aRequest.parameters.value,
+                       using: aRequest.parameters.using,
+                       element: aRequest.parameters.id,
+                       searchTimeout: this.searchTimeout
+                     },
+                     command_id);
+  },
+
   /**
    * Find elements using the indicated search strategy.
    *
@@ -1660,6 +1680,26 @@ MarionetteServerConnection.prototype = {
     }
   },
 
+  /**
+   * Find elements using the indicated search strategy
+   * starting from a known element. Used for WebDriver Compatibility only.
+   * @param  {object} aRequest
+   *         'using' member indicates which search method to use
+   *         'value' member is the value the client is looking for
+   *         'id' member is the value of the element to start from
+   */
+  findChildElements: function MDA_findChildElement(aRequest) {
+    let command_id = this.command_id = this.getCommandId();
+    this.sendAsync("findElementsContent",
+                    {
+                       value: aRequest.parameters.value,
+                       using: aRequest.parameters.using,
+                       element: aRequest.parameters.id,
+                       searchTimeout: this.searchTimeout
+                     },
+                     command_id);
+  },
+
   /**
    * Return the active element on the page
    */
@@ -2615,7 +2655,9 @@ MarionetteServerConnection.prototype.requestTypes = {
   "executeJSScript": MarionetteServerConnection.prototype.executeJSScript,
   "setSearchTimeout": MarionetteServerConnection.prototype.setSearchTimeout,
   "findElement": MarionetteServerConnection.prototype.findElement,
+  "findChildElement": MarionetteServerConnection.prototype.findChildElements, // Needed for WebDriver compat
   "findElements": MarionetteServerConnection.prototype.findElements,
+  "findChildElements":MarionetteServerConnection.prototype.findChildElements, // Needed for WebDriver compat
   "clickElement": MarionetteServerConnection.prototype.clickElement,
   "getElementAttribute": MarionetteServerConnection.prototype.getElementAttribute,
   "getElementText": MarionetteServerConnection.prototype.getElementText,