diff --git a/src/blockdev.c b/src/blockdev.c
index 2395c45..91879c4 100644
--- a/src/blockdev.c
+++ b/src/blockdev.c
@@ -32,7 +32,7 @@
 	}
 
 	part_start = 0;
-	part_length = device_size;
+	part_length = device_size / 512;
 
 	return 1;
 }
@@ -79,13 +79,13 @@
 {
 	if (start + size <= device_size) {
 		part_start = start;
-		part_length = size;
+		part_length = size / 512;
 	}
 }
 
 void dev_get_partition(unsigned long *start, unsigned long *size)
 {
 	*start = part_start;
-	*size = part_length;
+	*size = part_length * 512;
 }