diff --git a/fpdfsdk/BUILD.gn b/fpdfsdk/BUILD.gn
index 9eb9562..e0a9983 100644
--- a/fpdfsdk/BUILD.gn
+++ b/fpdfsdk/BUILD.gn
@@ -108,6 +108,7 @@
 
 pdfium_unittest_source_set("unittests") {
   sources = [
+    "cpdfsdk_helpers_unittest.cpp",
     "fpdf_annot_unittest.cpp",
     "fpdf_catalog_unittest.cpp",
     "fpdf_doc_unittest.cpp",