diff --git a/fpdfsdk/fpdf_attachment_embeddertest.cpp b/fpdfsdk/fpdf_attachment_embeddertest.cpp
index 6ab82f8..f2fd769 100644
--- a/fpdfsdk/fpdf_attachment_embeddertest.cpp
+++ b/fpdfsdk/fpdf_attachment_embeddertest.cpp
@@ -9,6 +9,7 @@
 #include "public/fpdf_attachment.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
+#include "testing/fx_string_testhelpers.h"
 #include "testing/utils/hash.h"
 
 static constexpr char kDateKey[] = "CreationDate";