diff --git a/xslt/epub2i5.xsl b/xslt/epub2i5.xsl
index d6d9aba..70d91a7 100644
--- a/xslt/epub2i5.xsl
+++ b/xslt/epub2i5.xsl
@@ -230,6 +230,10 @@
             <xsl:message terminate="yes">ERROR: No title found for ISBN: <xsl:value-of select="$isbn"/></xsl:message>
         </xsl:if>
 
+        <xsl:if test="not(normalize-space($autor))">
+            <xsl:message terminate="yes">ERROR: No author found for ISBN: <xsl:value-of select="$isbn"/></xsl:message>
+        </xsl:if>
+
         <idsDoc TEIform="TEI.2" type="text" version="1.0">
             <idsHeader TEIform="teiHeader" pattern="text" status="new" type="document" version="1.1">
                 <fileDesc>