diff --git a/mkfs/main.c b/mkfs/main.c
index 4c2ce98c7..00c6b7677 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -464,6 +464,8 @@ static const char * const mkfs_usage[] = {
 	OPTLINE("", "- default - the SUBDIR will be a subvolume and also set as default (can be specified only once)"),
 	OPTLINE("", "- default-ro - like 'default' and is created as read-only subvolume (can be specified only once)"),
 	OPTLINE("--shrink", "(with --rootdir) shrink the filled filesystem to minimal size"),
+	OPTLINE("--shrink-slack-size SIZE",
+		"(with --shrink) include extra slack space after shrinking (default 0)"),
 	OPTLINE("-K|--nodiscard", "do not perform whole device TRIM"),
 	OPTLINE("-f|--force", "force overwrite of existing filesystem"),
 	"",
@@ -1176,6 +1178,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 	int i;
 	bool ssd = false;
 	bool shrink_rootdir = false;
+	u64 shrink_slack_size = 0;
 	u64 source_dir_size = 0;
 	u64 min_dev_size;
 	u64 shrink_size;
@@ -1220,6 +1223,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 		int c;
 		enum {
 			GETOPT_VAL_SHRINK = GETOPT_VAL_FIRST,
+			GETOPT_VAL_SHRINK_SLACK_SIZE,
 			GETOPT_VAL_CHECKSUM,
 			GETOPT_VAL_GLOBAL_ROOTS,
 			GETOPT_VAL_DEVICE_UUID,
@@ -1250,6 +1254,8 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 			{ "quiet", 0, NULL, 'q' },
 			{ "verbose", 0, NULL, 'v' },
 			{ "shrink", no_argument, NULL, GETOPT_VAL_SHRINK },
+			{ "shrink-slack-size", required_argument, NULL,
+			  GETOPT_VAL_SHRINK_SLACK_SIZE },
 			{ "compress", required_argument, NULL,
 				GETOPT_VAL_COMPRESS },
 #if EXPERIMENTAL
@@ -1386,6 +1392,9 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 			case GETOPT_VAL_SHRINK:
 				shrink_rootdir = true;
 				break;
+			case GETOPT_VAL_SHRINK_SLACK_SIZE:
+				shrink_slack_size = arg_strtou64_with_suffix(optarg);
+				break;
 			case GETOPT_VAL_CHECKSUM:
 				csum_type = parse_csum_type(optarg);
 				break;
@@ -1433,6 +1442,12 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 		ret = 1;
 		goto error;
 	}
+	if (shrink_slack_size > 0 && !shrink_rootdir) {
+		error("the option --shrink-slack-size must be used with --shrink");
+		ret = 1;
+		goto error;
+
+	}
 	if (!list_empty(&subvols) && source_dir == NULL) {
 		error("option --subvol must be used with --rootdir");
 		ret = 1;
@@ -2104,8 +2119,17 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 
 		if (shrink_rootdir) {
 			pr_verbose(LOG_DEFAULT, "  Shrink:           yes\n");
+			if (shrink_slack_size > 0) {
+				pr_verbose(
+					LOG_DEFAULT,
+					"  Shrink slack:           %llu (%s)\n",
+					shrink_slack_size,
+					pretty_size(shrink_slack_size));
+			}
 			ret = btrfs_mkfs_shrink_fs(fs_info, &shrink_size,
-						   shrink_rootdir);
+						   shrink_rootdir,
+						   shrink_slack_size);
+
 			if (ret < 0) {
 				errno = -ret;
 				error("error while shrinking filesystem: %m");
diff --git a/mkfs/rootdir.c b/mkfs/rootdir.c
index 5f4cfb93c..c3e39036c 100644
--- a/mkfs/rootdir.c
+++ b/mkfs/rootdir.c
@@ -17,6 +17,8 @@
  */
 
 #include "kerncompat.h"
+#include <linux/fs.h>
+#include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/xattr.h>
 #include <dirent.h>
@@ -52,6 +54,7 @@
 #include "common/root-tree-utils.h"
 #include "common/path-utils.h"
 #include "common/rbtree-utils.h"
+#include "common/units.h"
 #include "mkfs/rootdir.h"
 
 #define LZO_LEN 4
@@ -1925,9 +1928,10 @@ static int set_device_size(struct btrfs_fs_info *fs_info,
 }
 
 int btrfs_mkfs_shrink_fs(struct btrfs_fs_info *fs_info, u64 *new_size_ret,
-			 bool shrink_file_size)
+			 bool shrink_file_size, u64 slack_size)
 {
 	u64 new_size;
+	u64 blk_device_size;
 	struct btrfs_device *device;
 	struct list_head *cur;
 	struct stat file_stat;
@@ -1955,6 +1959,14 @@ int btrfs_mkfs_shrink_fs(struct btrfs_fs_info *fs_info, u64 *new_size_ret,
 		return -EUCLEAN;
 	}
 
+	if (!IS_ALIGNED(slack_size, fs_info->sectorsize)) {
+		error("slack size %llu not aligned to %u",
+				slack_size, fs_info->sectorsize);
+		return -EUCLEAN;
+	}
+
+	new_size += slack_size;
+
 	device = list_entry(fs_info->fs_devices->devices.next,
 			   struct btrfs_device, dev_list);
 	ret = set_device_size(fs_info, device, new_size);
@@ -1969,6 +1981,15 @@ int btrfs_mkfs_shrink_fs(struct btrfs_fs_info *fs_info, u64 *new_size_ret,
 			error("failed to stat devid %llu: %m", device->devid);
 			return ret;
 		}
+		if (S_ISBLK(file_stat.st_mode)) {
+			ioctl(device->fd, BLKGETSIZE64, &blk_device_size);
+			if (blk_device_size < new_size) {
+				warning("blkdev size %llu (%s) is smaller than fs size %llu (%s)",
+					blk_device_size,
+					pretty_size(blk_device_size), new_size,
+					pretty_size(new_size));
+			}
+		}
 		if (!S_ISREG(file_stat.st_mode))
 			return ret;
 		ret = ftruncate(device->fd, new_size);
diff --git a/mkfs/rootdir.h b/mkfs/rootdir.h
index b32fda5bf..1eee38245 100644
--- a/mkfs/rootdir.h
+++ b/mkfs/rootdir.h
@@ -52,6 +52,6 @@ int btrfs_mkfs_fill_dir(struct btrfs_trans_handle *trans, const char *source_dir
 u64 btrfs_mkfs_size_dir(const char *dir_name, u32 sectorsize, u64 min_dev_size,
 			u64 meta_profile, u64 data_profile);
 int btrfs_mkfs_shrink_fs(struct btrfs_fs_info *fs_info, u64 *new_size_ret,
-			 bool shrink_file_size);
+			 bool shrink_file_size, u64 slack_size);
 
 #endif