--- a/devtools/client/webconsole/test/browser_webconsole_exception_stackframe.js
+++ b/devtools/client/webconsole/test/browser_webconsole_exception_stackframe.js
@@ -45,17 +45,17 @@ function test() {
       webconsole: hud,
       messages: [{
         text: "nonExistingMethodCall is not defined",
         category: CATEGORY_JS,
         severity: SEVERITY_ERROR,
         collapsible: true,
         stacktrace: stack,
       }, {
-        text: "An invalid or illegal string was specified",
+        text: "SyntaxError: 'buggy;selector' is not a valid selector",
         category: CATEGORY_JS,
         severity: SEVERITY_ERROR,
         collapsible: true,
         stacktrace: [{
           file: TEST_FILE,
           fn: "domAPI",
           line: 25,
         }, {

--- a/devtools/client/webconsole/test/browser_webconsole_output_04.js
+++ b/devtools/client/webconsole/test/browser_webconsole_output_04.js
@@ -53,19 +53,18 @@ var inputTests = [
     printOutput: '"TypeError: window.foobar is not a function"',
     inspectable: true,
     variablesViewLabel: "TypeError",
   },
 
   // 4
   {
     input: "testDOMException()",
-    output: 'DOMException [SyntaxError: "An invalid or illegal string was ' +
-            'specified"',
-    printOutput: '"SyntaxError: An invalid or illegal string was specified"',
+    output: `DOMException [SyntaxError: "'foo;()bar!' is not a valid selector"`,
+    printOutput: `"SyntaxError: 'foo;()bar!' is not a valid selector"`,
     inspectable: true,
     variablesViewLabel: "SyntaxError",
   },
 
   // 5
   {
     input: "testCSSStyleDeclaration()",
     output: 'CSS2Properties { color: "green", font-size: "2em" }',

--- a/devtools/shared/webconsole/test/test_jsterm_queryselector.html
+++ b/devtools/shared/webconsole/test/test_jsterm_queryselector.html
@@ -87,22 +87,22 @@ let checkQuerySelectorAllNotExist = Task
   nextTest();
 });
 
 let checkQuerySelectorAllException = Task.async(function*() {
   info ("$$ returns an exception if an invalid selector was provided");
   let response = yield evaluateJS("$$(':foo')");
   checkObject(response, {
     input: "$$(':foo')",
-    exceptionMessage: "SyntaxError: An invalid or illegal string was specified",
+    exceptionMessage: "SyntaxError: ':foo' is not a valid selector",
     exception: {
       preview: {
         kind: "DOMException",
         name: "SyntaxError",
-        message: "An invalid or illegal string was specified"
+        message: "':foo' is not a valid selector"
       }
     }
   });
   nextTest();
 });
 
 function basicResultCheck(response, input, output) {
   checkObject(response, {

--- a/dom/base/nsINode.cpp
+++ b/dom/base/nsINode.cpp
@@ -2701,33 +2701,43 @@ nsINode::ParseSelectorList(const nsAStri
 {
   nsIDocument* doc = OwnerDoc();
   nsIDocument::SelectorCache& cache = doc->GetSelectorCache();
   nsCSSSelectorList* selectorList = nullptr;
   bool haveCachedList = cache.GetList(aSelectorString, &selectorList);
   if (haveCachedList) {
     if (!selectorList) {
       // Invalid selector.
-      aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
+      aRv.ThrowDOMException(NS_ERROR_DOM_SYNTAX_ERR,
+        NS_LITERAL_CSTRING("'") + NS_ConvertUTF16toUTF8(aSelectorString) +
+        NS_LITERAL_CSTRING("' is not a valid selector")
+      );
     }
     return selectorList;
   }
 
   nsCSSParser parser(doc->CSSLoader());
 
   aRv = parser.ParseSelectorString(aSelectorString,
                                    doc->GetDocumentURI(),
                                    0, // XXXbz get the line number!
                                    &selectorList);
   if (aRv.Failed()) {
     // We hit this for syntax errors, which are quite common, so don't
     // use NS_ENSURE_SUCCESS.  (For example, jQuery has an extended set
     // of selectors, but it sees if we can parse them first.)
     MOZ_ASSERT(aRv.ErrorCodeIs(NS_ERROR_DOM_SYNTAX_ERR),
                "Unexpected error, so cached version won't return it");
+
+    // Change the error message to match above.
+    aRv.ThrowDOMException(NS_ERROR_DOM_SYNTAX_ERR,
+      NS_LITERAL_CSTRING("'") + NS_ConvertUTF16toUTF8(aSelectorString) +
+      NS_LITERAL_CSTRING("' is not a valid selector")
+    );
+
     cache.CacheList(aSelectorString, nullptr);
     return nullptr;
   }
 
   // Filter out pseudo-element selectors from selectorList
   nsCSSSelectorList** slot = &selectorList;
   do {
     nsCSSSelectorList* cur = *slot;