diff --git a/src/disk.sh b/src/disk.sh
index ac2a907..c4c03ac 100644
--- a/src/disk.sh
+++ b/src/disk.sh
@@ -376,7 +376,7 @@ createDevice () {
       result+=",if=none \
       -device nvme,drive=${DISK_ID}${index},serial=deadbeaf${DISK_INDEX}"
       echo "$result"
-      ;;      
+      ;;
     "ide" | "sata" )
       result+=",if=none \
       -device ich9-ahci,id=ahci${DISK_INDEX},addr=$DISK_ADDRESS \
@@ -470,12 +470,13 @@ addDisk () {
   [ -z "$DISK_SPACE" ] && DISK_SPACE="16G"
   DISK_SPACE=$(echo "${DISK_SPACE^^}" | sed 's/MB/M/g;s/GB/G/g;s/TB/T/g')
   [[ -z "${DISK_SPACE//[0-9]}" ]] && DISK_SPACE="${DISK_SPACE}G"
-  DATA_SIZE=$(numfmt --from=iec "$DISK_SPACE")
 
-  if (( DATA_SIZE < 1 )); then
+  if ! numfmt --from=iec "$DISK_SPACE" &>/dev/null; then
     error "Invalid value for ${DISK_DESC^^}_SIZE: $DISK_SPACE" && exit 73
   fi
 
+  DATA_SIZE=$(numfmt --from=iec "$DISK_SPACE")
+
   if (( DATA_SIZE < 104857600 )); then
     error "Please increase ${DISK_DESC^^}_SIZE to at least 100 MB." && exit 73
   fi