diff --git a/debian/mariadb-server-10.6.mariadb.init b/debian/mariadb-server-10.6.mariadb.init
index b2b7142084f..f68fbc99bc2 100644
--- a/debian/mariadb-server-10.6.mariadb.init
+++ b/debian/mariadb-server-10.6.mariadb.init
@@ -86,7 +86,7 @@ sanity_checks() {
   datadir=`mariadbd_get_param datadir`
   # As preset blocksize of GNU df is 1024 then available bytes is $df_available_blocks * 1024
   # 4096 blocks is then lower than 4 MB
-  df_available_blocks=`LC_ALL=C BLOCKSIZE= df --output=avail "$datadir" | tail -n 1`
+  df_available_blocks="$(LC_ALL=C BLOCKSIZE='' df --output=avail "$datadir" | tail -n 1)"
   if [ "$df_available_blocks" -lt "4096" ]; then
     log_failure_msg "$0: ERROR: The partition with $datadir is too full!"
     echo                "ERROR: The partition with $datadir is too full!" | $ERR_LOGGER
diff --git a/debian/mariadb-server-10.6.preinst b/debian/mariadb-server-10.6.preinst
index 9a31b5c636e..2513e3ab021 100644
--- a/debian/mariadb-server-10.6.preinst
+++ b/debian/mariadb-server-10.6.preinst
@@ -226,7 +226,7 @@ fi
 
 # As preset blocksize of GNU df is 1024 then available bytes is $df_available_blocks * 1024
 # 4096 blocks is then lower than 4 MB
-df_available_blocks=`LC_ALL=C BLOCKSIZE= df --output=avail "$datadir" | tail -n 1`
+df_available_blocks="$(LC_ALL=C BLOCKSIZE='' df --output=avail "$mysql_datadir" | tail -n 1)"
 if [ "$df_available_blocks" -lt "4096" ]
 then
   echo "ERROR: There's not enough space in $mysql_datadir/" 1>&2