diff --git a/CleanSpec.mk b/CleanSpec.mk
index b84e1b6..73e51b9 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -44,6 +44,7 @@
 #$(call add-clean-step, find $(OUT_DIR) -type f -name "IGTalkSession*" -print0 | xargs -0 rm -f)
 #$(call add-clean-step, rm -rf $(PRODUCT_OUT)/data/*)
 
+$(call add-clean-step, rm -f $(PRODUCT_OUT)/system.img $(PRODUCT_OUT)/userdata.img)
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************
diff --git a/ext4_utils/mkuserimg.sh b/ext4_utils/mkuserimg.sh
index 2485085..3f2d2d4 100755
--- a/ext4_utils/mkuserimg.sh
+++ b/ext4_utils/mkuserimg.sh
@@ -5,12 +5,18 @@
 function usage() {
 cat<<EOT
 Usage:
-mkuserimg.sh SRC_DIR OUTPUT_FILE EXT_VARIANT MOUNT_POINT SIZE
+mkuserimg.sh [-s] SRC_DIR OUTPUT_FILE EXT_VARIANT MOUNT_POINT SIZE
 EOT
 }
 
 echo "in mkuserimg.sh PATH=$PATH"
 
+ENABLE_SPARSE_IMAGE=
+if [ "$1" = "-s" ]; then
+  ENABLE_SPARSE_IMAGE="-s"
+  shift
+fi
+
 if [ $# -ne 4 -a $# -ne 5 ]; then
   usage
   exit 1
@@ -41,8 +47,9 @@
     SIZE=128M
 fi
 
-echo "make_ext4fs -l $SIZE -a $MOUNT_POINT $OUTPUT_FILE $SRC_DIR"
-make_ext4fs -l $SIZE -a $MOUNT_POINT $OUTPUT_FILE $SRC_DIR
+MAKE_EXT4FS_CMD="make_ext4fs $ENABLE_SPARSE_IMAGE -l $SIZE -a $MOUNT_POINT $OUTPUT_FILE $SRC_DIR"
+echo $MAKE_EXT4FS_CMD
+$MAKE_EXT4FS_CMD
 if [ $? -ne 0 ]; then
   exit 4
 fi