diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index ded66f76..538500e7 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -465,9 +465,9 @@ endif()
 
 set(runtime_headers)
 foreach(f ${CORE_D_HEADERS})
-    dc_header(${f} ${D_FLAGS} runtime_headers)
+    dc_header(${f} "${D_FLAGS}" runtime_headers)
 endforeach()
-add_custom_target(build_headers DEPENDS ${runtime_headers})
+add_custom_target(build_headers ALL DEPENDS ${runtime_headers})
 
 #
 # Install target (libraries are automatically included).