diff --git a/poky/scripts/lib/wic/partition.py b/poky/scripts/lib/wic/partition.py
index ab304f1..a258340 100644
--- a/poky/scripts/lib/wic/partition.py
+++ b/poky/scripts/lib/wic/partition.py
@@ -105,7 +105,7 @@
                 extra_blocks = self.extra_space
 
             rootfs_size = actual_rootfs_size + extra_blocks
-            rootfs_size *= self.overhead_factor
+            rootfs_size = int(rootfs_size * self.overhead_factor)
 
             logger.debug("Added %d extra blocks to %s to get to %d total blocks",
                          extra_blocks, self.mountpoint, rootfs_size)