diff --git a/src/disk.sh b/src/disk.sh
index 6002ddf..c930835 100644
--- a/src/disk.sh
+++ b/src/disk.sh
@@ -8,7 +8,7 @@ set -Eeuo pipefail
 : "${DISK_TYPE:=""}"              # Device type to be used, "sata", "nvme", "blk" or "scsi"
 : "${DISK_FLAGS:=""}"             # Specifies the options for use with the qcow2 disk format
 : "${DISK_CACHE:="none"}"         # Caching mode, can be set to 'writeback' for better performance
-: "${DISK_DISCARD:="on"}"         # Controls whether unmap (TRIM) commands are passed to the host.
+: "${DISK_DISCARD:="unmap"}"      # Controls whether unmap (TRIM) commands are passed to the host.
 : "${DISK_ROTATION:="1"}"         # Rotation rate, set to 1 for SSD storage and increase for HDD
 
 # Sanitize all variables
@@ -663,6 +663,23 @@ if [[ "${DISK_IO,,}" == "native" && "${DISK_CACHE,,}" != "none" && "${DISK_CACHE
   DISK_IO="threads"
 fi
 
+case "${DISK_DISCARD,,}" in
+  "y" | "yes" | "true" | "1" | "on" | "unmap" )
+    DISK_DISCARD="unmap" ;;
+
+  "n" | "no" | "false" | "0" | "off" | "ignore" )
+    DISK_DISCARD="ignore" ;;
+
+  * )
+    warn "Invalid DISK_DISCARD value '$DISK_DISCARD', using 'unmap'."
+    DISK_DISCARD="unmap" ;;
+esac
+
+if [[ ! "$DISK_ROTATION" =~ ^[0-9]+$ ]]; then
+  warn "Invalid DISK_ROTATION value '$DISK_ROTATION', using 1."
+  DISK_ROTATION="1"
+fi
+
 case "${DISK_TYPE,,}" in
   "ide" | "sata" | "nvme" | "usb" | "scsi" | "blk" | "auto" | "none" ) ;;
   * ) error "Invalid DISK_TYPE specified, value \"$DISK_TYPE\" is not recognized!" && exit 80 ;;