diff --git a/clang-tools-extra/clangd/Context.cpp b/clang-tools-extra/clangd/Context.cpp
index 0a1bacd70618..23006778f550 100644
--- a/clang-tools-extra/clangd/Context.cpp
+++ b/clang-tools-extra/clangd/Context.cpp
@@ -19,6 +19,7 @@
 // It requires support from the runtime: __cxa_thread_atexit.
 // Rather than detect this, we use the pthread API where available.
 #include <pthread.h>
+#include <cstring>
 static clang::clangd::Context &currentContext() {
   using clang::clangd::Context;
   static pthread_key_t CtxKey;