diff --git a/src/languages/cpp.js b/src/languages/cpp.js
index edfbf1cd51..970f584bb3 100644
--- a/src/languages/cpp.js
+++ b/src/languages/cpp.js
@@ -302,7 +302,7 @@ export default function(hljs) {
     end: /[{;=]/,
     excludeEnd: true,
     keywords: CPP_KEYWORDS,
-    illegal: /[^\w\s\*&:<>.]/,
+    illegal: /[^\w\s\*&:<>.,]/,
     contains: [
       { // to prevent it from being confused as the function title
         begin: DECLTYPE_AUTO_RE,
diff --git a/test/markup/cpp/function-declarations.expect.txt b/test/markup/cpp/function-declarations.expect.txt
index fc7cea4c16..b04c01e87f 100644
--- a/test/markup/cpp/function-declarations.expect.txt
+++ b/test/markup/cpp/function-declarations.expect.txt
@@ -21,3 +21,5 @@
 
 <span class="hljs-function"><span class="hljs-keyword">void</span> <span class="hljs-title">A</span><span class="hljs-params">()</span>: a(<span class="hljs-number">10</span>) {</span>}
 <span class="hljs-function"><span class="hljs-keyword">explicit</span> <span class="hljs-title">A</span><span class="hljs-params">()</span>: a(<span class="hljs-number">10</span>) {</span>}
+
+<span class="hljs-function"><span class="hljs-keyword">extern</span> <span class="hljs-keyword">void</span> <span class="hljs-title">f</span><span class="hljs-params">(<span class="hljs-keyword">int</span>)</span>, <span class="hljs-title">g</span><span class="hljs-params">(<span class="hljs-keyword">char</span>)</span></span>;
diff --git a/test/markup/cpp/function-declarations.txt b/test/markup/cpp/function-declarations.txt
index ced198b2c7..c78ffc21a7 100644
--- a/test/markup/cpp/function-declarations.txt
+++ b/test/markup/cpp/function-declarations.txt
@@ -21,3 +21,5 @@ test();
 
 void A(): a(10) {}
 explicit A(): a(10) {}
+
+extern void f(int), g(char);