diff --git a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
index f7665ad20e9cc..02d248497d9d8 100644
--- a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
@@ -432,6 +432,7 @@ if (current_toolchain == default_toolchain) {
       "__format/range_default_formatter.h",
       "__format/range_formatter.h",
       "__format/unicode.h",
+      "__format/width_estimation_table.h",
       "__functional/binary_function.h",
       "__functional/binary_negate.h",
       "__functional/bind.h",