diff --git a/exercises/04/vslc/vsl_programs/Makefile b/exercises/04/vslc/vsl_programs/Makefile
index d526e29..6a38848 100644
--- a/exercises/04/vslc/vsl_programs/Makefile
+++ b/exercises/04/vslc/vsl_programs/Makefile
@@ -9,8 +9,8 @@ ps2: $(PS2_EXAMPLES)
 ps3: $(PS3_EXAMPLES)
 ps4: $(PS4_EXAMPLES)
 
-%.ast: %.vsl
-	$(VSLC) -t < $^ > $@
+%.ast: %.vsl clean
+	$(VSLC) -t -T -s < $^ > $@
 
 clean:
 	-rm -r */*.ast