diff --git a/toolchain/lexer/tokenized_buffer_test.cpp b/toolchain/lexer/tokenized_buffer_test.cpp
index bdbf4334430e..0656151c481f 100644
--- a/toolchain/lexer/tokenized_buffer_test.cpp
+++ b/toolchain/lexer/tokenized_buffer_test.cpp
@@ -7,6 +7,7 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
+#include <forward_list>
 #include <iterator>
 
 #include "llvm/ADT/ArrayRef.h"