diff --git a/make-includes/build_misc_rules.make b/make-includes/build_misc_rules.make
index eeab387..97c9864 100755
--- a/make-includes/build_misc_rules.make
+++ b/make-includes/build_misc_rules.make
@@ -93,10 +93,17 @@
 # document cross references, but won't get regenerated if the final target
 # PDF files exist. They will be caught by by the "clean" target though.
 #
-TIDY_FILES+=*.tmp *.out *.log *.nav *.toc *.snm *.head *.dvi \
-	*-derived.xml *.tex
-CLEAN_FILES+=*.aux *.pdf *.html $(IMGDIR)/*-print.pdf $(IMGDIR)/*-web.png
-
+TIDY_FILES+=*.tmp *.out *.log *.nav *.toc *.snm *.head *.dvi *-derived.xml
+CLEAN_FILES+=*.aux $(IMGDIR)/*-print.pdf $(IMGDIR)/*-web.png
+ifdef HAS_ANSWERS
+TIDY_FILES+=$(PRINT_QUESTIONS_TEX) $(PRINT_ANSWERS_TEX)
+CLEAN_FILES+=$(WEB_QUESTIONS_HTML) $(WEB_ANSWERS_HTML) \
+	$(PRINT_QUESTIONS_PDF_1UP) $(PRINT_ANSWERS_PDF_1UP) \
+	$(PRINT_QUESTIONS_PDF_2UP) $(PRINT_ANSWERS_PDF_2UP)
+else
+TIDY_FILES+=$(PRINT_TEX)
+CLEAN_FILES+=$(WEB_HTML) $(PRINT_PDF_1UP) $(PRINT_PDF_2UP)
+endif
 
 ################################################################################
 #