diff --git a/common/content/options.js b/common/content/options.js
index 843c413c..1f06f7e0 100644
--- a/common/content/options.js
+++ b/common/content/options.js
@@ -8,11 +8,7 @@
 
 /** @scope modules */
 
-let ValueError = Class("ValueError", Error, {
-    init: function (message) {
-        update(this, Error(message));
-    }
-});
+let ValueError = Class("ValueError", ErrorBase);
 
 // do NOT create instances of this class yourself, use the helper method
 // options.add() instead
diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index f0b4048c..35ff5875 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -176,7 +176,7 @@ function require(obj, name, from) {
 defineModule("base", {
     // sed -n 's/^(const|function) ([a-zA-Z0-9_]+).*/	"\2",/p' base.jsm | sort | fmt
     exports: [
-        "Cc", "Ci", "Class", "Cr", "Cu", "Module", "Object", "Runnable",
+        "ErrorBase", "Cc", "Ci", "Class", "Cr", "Cu", "Module", "Object", "Runnable",
         "Struct", "StructBase", "Timer", "UTF8", "XPCOM", "XPCOMUtils", "array",
         "call", "callable", "ctypes", "curry", "debuggerProperties", "defineModule",
         "deprecated", "endModule", "forEach", "isArray", "isGenerator",
@@ -857,6 +857,26 @@ function XPCOM(interfaces, superClass) {
     return res;
 }
 
+/**
+ * An abstract base class for classes that wish to inherit from Error.
+ */
+const ErrorBase = Class("ErrorBase", Error, {
+    level: 2,
+    init: function (message, level) {
+        level = level || 0;
+        update(this, Error(message))
+        this.message = message;
+
+        let frame = Components.stack;
+        for (let i = 0; i < this.level + level; i++) {
+            frame = frame.caller;
+            this.stack = this.stack.replace(/^.*\n/, "");
+        }
+        this.fileName = frame.filename;
+        this.lineNumber = frame.lineNumber;
+    }
+});
+
 /**
  * Constructs a new Module class and instantiates an instance into the current
  * module global object.
diff --git a/common/modules/util.jsm b/common/modules/util.jsm
index a5c12827..83505ecb 100644
--- a/common/modules/util.jsm
+++ b/common/modules/util.jsm
@@ -28,12 +28,7 @@ memoize(this, "Commands", function () {
     return obj.Commands;
 });
 
-const FailedAssertion = Class("FailedAssertion", Error, {
-    init: function (message) {
-        update(this, Error(message))
-        this.message = message;
-    }
-});
+const FailedAssertion = Class("FailedAssertion", ErrorBase);
 
 function wrapCallback(fn)
     fn.wrapper = function wrappedCallback () {
@@ -125,7 +120,7 @@ const Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference])
      */
     assert: function (condition, message) {
         if (!condition)
-            throw FailedAssertion(message);
+            throw FailedAssertion(message, 1);
     },
 
     get chromePackages() {