diff --git a/configs/sipeed_maix_bit_sdcard_defconfig b/configs/sipeed_maix_bit_sdcard_defconfig
index 4ad3b2e1db..e42c3ee425 100644
--- a/configs/sipeed_maix_bit_sdcard_defconfig
+++ b/configs/sipeed_maix_bit_sdcard_defconfig
@@ -36,7 +36,7 @@ BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
 # Filesystem
 BR2_INIT_NONE=y
 BR2_TARGET_ROOTFS_EXT2=y
-BR2_TARGET_ROOTFS_EXT2_SIZE=64M
+BR2_TARGET_ROOTFS_EXT2_SIZE="64M"
 BR2_ROOTFS_OVERLAY="board/canaan/k210-soc/rootfs_overlay"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/canaan/k210-soc/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
diff --git a/configs/sipeed_maix_dock_sdcard_defconfig b/configs/sipeed_maix_dock_sdcard_defconfig
index de79ff950b..d1a1b2886d 100644
--- a/configs/sipeed_maix_dock_sdcard_defconfig
+++ b/configs/sipeed_maix_dock_sdcard_defconfig
@@ -36,7 +36,7 @@ BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
 # Filesystem
 BR2_INIT_NONE=y
 BR2_TARGET_ROOTFS_EXT2=y
-BR2_TARGET_ROOTFS_EXT2_SIZE=64M
+BR2_TARGET_ROOTFS_EXT2_SIZE="64M"
 BR2_ROOTFS_OVERLAY="board/canaan/k210-soc/rootfs_overlay"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/canaan/k210-soc/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
diff --git a/configs/sipeed_maix_go_sdcard_defconfig b/configs/sipeed_maix_go_sdcard_defconfig
index 7338b0c09d..65a6815c20 100644
--- a/configs/sipeed_maix_go_sdcard_defconfig
+++ b/configs/sipeed_maix_go_sdcard_defconfig
@@ -36,7 +36,7 @@ BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
 # Filesystem
 BR2_INIT_NONE=y
 BR2_TARGET_ROOTFS_EXT2=y
-BR2_TARGET_ROOTFS_EXT2_SIZE=64M
+BR2_TARGET_ROOTFS_EXT2_SIZE="64M"
 BR2_ROOTFS_OVERLAY="board/canaan/k210-soc/rootfs_overlay"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/canaan/k210-soc/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
diff --git a/configs/sipeed_maixduino_sdcard_defconfig b/configs/sipeed_maixduino_sdcard_defconfig
index b4f1994239..5785d7acf3 100644
--- a/configs/sipeed_maixduino_sdcard_defconfig
+++ b/configs/sipeed_maixduino_sdcard_defconfig
@@ -36,7 +36,7 @@ BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
 # Filesystem
 BR2_INIT_NONE=y
 BR2_TARGET_ROOTFS_EXT2=y
-BR2_TARGET_ROOTFS_EXT2_SIZE=64M
+BR2_TARGET_ROOTFS_EXT2_SIZE="64M"
 BR2_ROOTFS_OVERLAY="board/canaan/k210-soc/rootfs_overlay"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/canaan/k210-soc/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"