diff --git a/Makefile b/Makefile
index 4deb7fc..808246c 100644
--- a/Makefile
+++ b/Makefile
@@ -70,7 +70,7 @@
 	mkdir -p $(TARGET_DIR)
 	echo "Converting $< to $@"
 	$(SAXON) -xsl:xslt/epub2i5.xsl $(shell find $< -name "*.opf")  $(shell if cat `find $< -name originalPath.xml` | grep -iq buchpreis; then echo buchpreis=1; fi)> $@ || \
-	(sleep 5 && $(SAXON) -xsl:xslt/epub2i5.xsl $(shell find $< -name "*.opf") $(shell if cat `find $< -name originalPath.xml` | grep -iq buchpreis; then echo buchpreis=1; fi) > $@) || (echo "WARN: ignoring invalid $@" && > $@)
+	(sleep 5 && $(SAXON) -xsl:xslt/epub2i5.xsl $(shell find $< -name "*.opf") $(shell if cat `find $< -name originalPath.xml` | grep -iq buchpreis; then echo buchpreis=1; fi) debug=1 > $@) || (echo "WARN: ignoring invalid $@" && > $@)
 
 
 %.zip: %.i5.xml