diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index e1374d9e1..32d8db0bb 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -80,6 +80,7 @@ if(NOT UNBOUND_INCLUDE_DIR OR STATIC)
   # be set in this case.
   # The unbound CMakeLists.txt can set it, since it's also needed for the
   # static OpenSSL libraries set up there after with target_link_libraries.
+  add_subdirectory(unbound)
 
   set(UNBOUND_STATIC true PARENT_SCOPE)
   set(UNBOUND_INCLUDE "${CMAKE_CURRENT_SOURCE_DIR}/unbound/libunbound" PARENT_SCOPE)