diff --git a/compilerplugins/clang/test/mapindex.cxx b/compilerplugins/clang/test/mapindex.cxx
index 68261df500dd..de7dd2590220 100644
--- a/compilerplugins/clang/test/mapindex.cxx
+++ b/compilerplugins/clang/test/mapindex.cxx
@@ -9,6 +9,7 @@
 
 #include <map>
 #include <memory>
+#include <string>
 
 struct CallbackFlushHandler
 {