diff --git a/runtime/syntax/cpp.yaml b/runtime/syntax/cpp.yaml
index f5d6e68945..dbdefd938d 100644
--- a/runtime/syntax/cpp.yaml
+++ b/runtime/syntax/cpp.yaml
@@ -2,7 +2,7 @@ filetype: c++
 
 detect:
     filename: "(\\.c(c|pp|xx)$|\\.h(h|pp|xx)?$|\\.ii?$|\\.(def)$)"
-    signature: "namespace|template|public|protected|private"
+    signature: "\\b(namespace|class|public|protected|private|template|constexpr|noexcept|nullptr|throw)\\b"
 
 rules:
     - identifier: "\\b[A-Z_][0-9A-Z_]*\\b"