--- doc/headers/Makefile.am
+++ doc/headers/Makefile.am
@@ -23,5 +23,6 @@
 
 copy_headers:
 	cp -f $(top_srcdir)/CUnit/Headers/*.h .
+	cp -f $(top_builddir)/CUnit/Headers/*.h .
 	cp -f $(top_srcdir)/CUnit/Sources/Win/Win.h .