diff --git a/Makefile b/Makefile
index 707740c..a15d5be 100644
--- a/Makefile
+++ b/Makefile
@@ -43,7 +43,7 @@
 $(TARGET_DIR)/%.i5.xml: $(BUILD_DIR)/% xslt/epub2i5.xsl xslt/idsCorpus-template.xml
 	mkdir -p $(TARGET_DIR)
 	echo "Converting $< to $@"
-	java -jar lib/saxon9ee.jar -xsl:xslt/epub2i5.xsl $(shell find $< -name content.opf) > $@
+	java -jar lib/saxon9ee.jar -xsl:xslt/epub2i5.xsl $(shell find $< -name "*.opf") > $@
 
 %.zip: %.i5.xml
 	tei2korapxml -l warn -s -tk - < $< > $@