diff --git a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
index 08075f3cc20..e97861c639d 100644
--- a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
@@ -24,6 +24,7 @@
 #include <algorithm>
 #include <map>
 #include <memory>
+#include <string>
 #include <type_traits>
 #include <utility>
 #include <vector>