--- a/testing/marionette/error.js
+++ b/testing/marionette/error.js
@@ -43,16 +43,17 @@ const BUILTIN_ERRORS = new Set([
   "SyntaxError",
   "TypeError",
   "URIError",
 ]);
 
 this.EXPORTED_SYMBOLS = [
   "error",
   "pprint",
+  "stack",
 ].concat(Array.from(ERRORS));
 
 /** @namespace */
 this.error = {};
 
 /**
  * Check if |val| is an instance of the |Error| prototype.
  *
@@ -210,16 +211,24 @@ this.pprint = function(ss, ...values) {
         s = typeof val;
       }
       res.push(s);
     }
   }
   return res.join("");
 };
 
+/** Create a stacktrace to the current line in the program. */
+this.stack = function() {
+  let trace = new Error().stack;
+  let sa = trace.split("\n");
+  sa = sa.slice(1);
+  return "stacktrace:\n" + sa.join("\n");
+};
+
 /**
  * WebDriverError is the prototypal parent of all WebDriver errors.
  * It should not be used directly, as it does not correspond to a real
  * error in the specification.
  */
 class WebDriverError extends Error {
   /**
    * @param {(string|Error)=} x

--- a/testing/marionette/test_error.js
+++ b/testing/marionette/test_error.js
@@ -19,16 +19,17 @@ const {
   MoveTargetOutOfBoundsError,
   NoAlertOpenError,
   NoSuchElementError,
   NoSuchFrameError,
   NoSuchWindowError,
   pprint,
   ScriptTimeoutError,
   SessionNotCreatedError,
+  stack,
   StaleElementReferenceError,
   TimeoutError,
   UnableToSetCookieError,
   UnexpectedAlertOpenError,
   UnknownCommandError,
   UnknownError,
   UnsupportedOperationError,
   WebDriverError,
@@ -139,16 +140,24 @@ add_test(function test_pprint() {
     classList: {length: 1},
     className: "bar baz",
   };
   equal('<input id="foo" class="bar baz">', pprint`${el}`);
 
   run_next_test();
 });
 
+add_test(function test_stack() {
+  equal("string", typeof stack());
+  ok(stack().includes("test_stack"));
+  ok(!stack().includes("add_test"));
+
+  run_next_test();
+});
+
 add_test(function test_toJSON() {
   let e0 = new WebDriverError();
   let e0s = e0.toJSON();
   equal(e0s.error, "webdriver error");
   equal(e0s.message, "");
   equal(e0s.stacktrace, e0.stack);
 
   let e1 = new WebDriverError("a");