diff --git a/lib/cmdlinepart.c b/lib/cmdlinepart.c
index d7d4441..5b9f33c 100644
--- a/lib/cmdlinepart.c
+++ b/lib/cmdlinepart.c
@@ -101,6 +101,9 @@
 	loff_t offset = 0;
 	int ret;
 
+	if (!parts || *parts == '\0')
+		return 0;
+
 	while (1) {
 		loff_t size = 0;