diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 6593aaf..6937239 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -1248,3 +1248,5 @@
 neat: clean
 	rm -f $(all_final)
 .PHONY: clean neat
+
+.SECONDARY: $(all_intermediate)