diff --git a/transport/HidlPassthroughSupport.cpp b/transport/HidlPassthroughSupport.cpp
index e5eb164..c5ca1c9 100644
--- a/transport/HidlPassthroughSupport.cpp
+++ b/transport/HidlPassthroughSupport.cpp
@@ -25,6 +25,9 @@
 namespace hardware {
 namespace details {
 
+// TODO(b/69122224) remove once prebuilts are updated.
+extern BsConstructorMap gBsConstructorMap;
+
 static sp<IBase> tryWrap(const std::string& descriptor, sp<IBase> iface) {
     auto func = getBsConstructorMap().get(descriptor, nullptr);
     if (!func) {