diff --git a/src/languages/cpp.js b/src/languages/cpp.js
index 1b3e337784..199fb9c99f 100644
--- a/src/languages/cpp.js
+++ b/src/languages/cpp.js
@@ -112,7 +112,8 @@ export default function(hljs) {
         begin: /<.*?>/
       },
       C_LINE_COMMENT_MODE,
-      hljs.C_BLOCK_COMMENT_MODE
+      hljs.C_BLOCK_COMMENT_MODE,
+      NUMBERS
     ]
   };
 
diff --git a/test/markup/cpp/preprocessor.txt b/test/markup/cpp/preprocessor.txt
index 69964a8768..810e5a8e90 100644
--- a/test/markup/cpp/preprocessor.txt
+++ b/test/markup/cpp/preprocessor.txt
@@ -28,6 +28,10 @@ if (p) {
 #endif
 }
 
+// Test : digit separators in integer literals
+#define MILLION 1'000'000
+int x = 1'000'000;
+
 // this is a continued\
 comment.
 end