diff --git a/mkimg.sh b/mkimg.sh
index 92b53ce..4e41849 100644
--- a/mkimg.sh
+++ b/mkimg.sh
@@ -29,7 +29,7 @@ ROOT_SIZE=$((TOTAL_SIZE - BOOT_SIZE))
 
 # Extend to reserve some free space.
 BOOT_SIZE=$((BOOT_SIZE * 2))
-ROOT_SIZE=$((ROOT_SIZE + 10 * 1024 * 1024 * 1024))
+ROOT_SIZE=$((ROOT_SIZE + 4 * 1024 * 1024 * 1024))
 
 BLOCK_SIZE=512