--- file_not_specified_in_diff	
+++ file_not_specified_in_diff	
@@ -, +, @@ 
--- mozextension.eclass
+++ mozextension.eclass
@@ -48,7 +48,8 @@ 
 	x="${1}"
 	cd ${x}
 	# determine id for extension
-	emid=$(sed -n -e '/<\?em:id>\?/!d; s/.*\([\"{].*[}\"]\).*/\1/; s/\"//g; p; q' ${x}/install.rdf) || die "failed to determine extension id"
+	emid=$(sed -n -e '/install-manifest/,$ { /<\?em:id>\?/!d; s/.*\([\"{].*[}\"]\).*/\1/; s/\"//g; p; q }' ${x}/install.rdf) \
+		&& [ -n "${emid}" ] || die "failed to determine extension id"
 	insinto "${MOZILLA_FIVE_HOME}"/extensions/${emid}
 	doins -r "${x}"/* || die "failed to copy extension"
 }