diff --git a/core/main.mk b/core/main.mk
index 618594b..e20f669 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -1353,7 +1353,9 @@
     $(eval whitelist_patterns := $(call resolve-product-relative-paths,$(whitelist))) \
     $(eval files := $(call product-installed-files, $(makefile))) \
     $(eval offending_files := $(filter-out $(path_patterns) $(whitelist_patterns) $(static_whitelist_patterns),$(files))) \
-    $(call maybe-print-list-and-error,$(offending_files),$(makefile) produces files outside its artifact path requirement.) \
+    $(call maybe-print-list-and-error,$(offending_files),\
+      $(makefile) produces files outside its artifact path requirement. \
+      Allowed paths are $(subst $(space),$(comma)$(space),$(addsuffix *,$(requirements)))) \
     $(eval unused_whitelist := $(filter-out $(files),$(whitelist_patterns))) \
     $(call maybe-print-list-and-error,$(unused_whitelist),$(makefile) includes redundant whitelist entries in its artifact path requirement.) \
     $(eval ### Optionally verify that nothing else produces files inside this artifact path requirement.) \