--- a/addon-sdk/source/test/test-sandbox.js
+++ b/addon-sdk/source/test/test-sandbox.js
@@ -52,17 +52,17 @@ exports['test exceptions'] = function(as
   let fixture = sandbox();
   try {
     evaluate(fixture, '!' + function() {
       var message = 'boom';
       throw Error(message);
     } + '();');
   }
   catch (error) {
-    assert.equal(error.fileName, '', 'no fileName reported');
+    assert.equal(error.fileName, '[System Principal]', 'No specific fileName reported');
     assert.equal(error.lineNumber, 3, 'reports correct line number');
   }
 
   try {
     evaluate(fixture, '!' + function() {
       var message = 'boom';
       throw Error(message);
     } + '();', 'foo.js');

--- a/caps/nsPrincipal.cpp
+++ b/caps/nsPrincipal.cpp
@@ -975,18 +975,31 @@ nsExpandedPrincipal::IsOnCSSUnprefixingW
   // for an expanded principal. (And probably shouldn't be needed.)
   return false;
 }
 
 
 void
 nsExpandedPrincipal::GetScriptLocation(nsACString& aStr)
 {
-  // Is that a good idea to list it's principals?
   aStr.Assign(EXPANDED_PRINCIPAL_SPEC);
+  aStr.AppendLiteral(" (");
+
+  for (size_t i = 0; i < mPrincipals.Length(); ++i) {
+    if (i != 0) {
+      aStr.AppendLiteral(", ");
+    }
+
+    nsAutoCString spec;
+    nsJSPrincipals::get(mPrincipals.ElementAt(i))->GetScriptLocation(spec);
+
+    aStr.Append(spec);
+
+  }
+  aStr.Append(")");
 }
 
 #ifdef DEBUG
 void nsExpandedPrincipal::dumpImpl()
 {
   fprintf(stderr, "nsExpandedPrincipal (%p)\n", static_cast<void*>(this));
 }
 #endif 

--- a/js/xpconnect/src/Sandbox.cpp
+++ b/js/xpconnect/src/Sandbox.cpp
@@ -1502,17 +1502,17 @@ xpc::EvalInSandbox(JSContext* cx, Handle
     nsIScriptObjectPrincipal* sop =
         static_cast<nsIScriptObjectPrincipal*>(xpc_GetJSPrivate(sandbox));
     MOZ_ASSERT(sop, "Invalid sandbox passed");
     SandboxPrivate* priv = static_cast<SandboxPrivate*>(sop);
     nsCOMPtr<nsIPrincipal> prin = sop->GetPrincipal();
     NS_ENSURE_TRUE(prin, NS_ERROR_FAILURE);
 
     nsAutoCString filenameBuf;
-    if (!filename.IsVoid()) {
+    if (!filename.IsVoid() && filename.Length() != 0) {
         filenameBuf.Assign(filename);
     } else {
         // Default to the spec of the principal.
         nsJSPrincipals::get(prin)->GetScriptLocation(filenameBuf);
         lineNo = 1;
     }
 
     // We create a separate cx to do the sandbox evaluation. Scope it.

new file mode 100644
--- /dev/null
+++ b/js/xpconnect/tests/unit/test_sandbox_name.js
@@ -0,0 +1,28 @@
+"use strict";
+
+const { utils: Cu, interfaces: Ci, classes: Cc } = Components;
+
+/**
+ * Test that the name of a sandbox contains the name of all principals.
+ */
+function test_sandbox_name() {
+  let names = [
+    "http://example.com/?" + Math.random(),
+    "http://example.org/?" + Math.random()
+  ];
+  let sandbox = Cu.Sandbox(names);
+  let fileName = Cu.evalInSandbox(
+    "(new Error()).fileName",
+    sandbox,
+    "latest" /*js version*/,
+    ""/*file name*/
+  );
+
+  for (let name of names) {
+    Assert.ok(fileName.indexOf(name) != -1, `Name ${name} appears in ${fileName}`);
+  }
+};
+
+function run_test() {
+  test_sandbox_name();
+}

--- a/js/xpconnect/tests/unit/xpcshell.ini
+++ b/js/xpconnect/tests/unit/xpcshell.ini
@@ -94,16 +94,17 @@ skip-if = os == "android" # native test 
 [test_url.js]
 [test_URLSearchParams.js]
 [test_crypto.js]
 [test_css.js]
 [test_rtcIdentityProvider.js]
 [test_sandbox_atob.js]
 [test_isProxy.js]
 [test_getObjectPrincipal.js]
+[test_sandbox_name.js]
 [test_watchdog_enable.js]
 head = head_watchdog.js
 [test_watchdog_disable.js]
 head = head_watchdog.js
 [test_watchdog_toggle.js]
 head = head_watchdog.js
 [test_watchdog_default.js]
 head = head_watchdog.js