diff --git a/src/install.sh b/src/install.sh
index 852cdad..c3739b5 100644
--- a/src/install.sh
+++ b/src/install.sh
@@ -1,36 +1,31 @@
 #!/usr/bin/env bash
 set -Eeuo pipefail
 
-file=$(find / -maxdepth 1 -type f -iname boot.iso | head -n 1)
-[ ! -s "$file" ] && file=$(find "$STORAGE" -maxdepth 1 -type f -iname boot.iso | head -n 1)
+iso () {
+  local file="$1"
+  [ ! -f "$file" ] && return 1
+  [ ! -s "$file" ] && return 1
 
-if [ -f "$file" ] && [ -s "$file" ]; then
   BOOT="$file"
   return 0
-fi
+}
 
-if [ -z "$BOOT" ]; then
+file=$(find / -maxdepth 1 -type f -iname boot.iso | head -n 1)
+[ ! -s "$file" ] && file=$(find "$STORAGE" -maxdepth 1 -type f -iname boot.iso | head -n 1)
+iso "$file" && return 0
+
+if [ -z "$BOOT" ] || [[ "$BOOT" == *"example.com/image.iso" ]]; then
   hasDisk && return 0
   error "No boot disk specified, set BOOT= to the URL of an ISO file." && exit 64
 fi
 
 base=$(basename "$BOOT")
-file="$STORAGE/$base" 
-
-if [ -f "$file" ] && [ -s "$file" ]; then
-  BOOT="$file"
-  return 0
-fi
+iso "$STORAGE/$base" && return 0
 
 base=$(basename "${BOOT%%\?*}")
 : "${base//+/ }"; printf -v base '%b' "${_//%/\\x}"
 base=$(echo "$base" | sed -e 's/[^A-Za-z0-9._-]/_/g')
-file="$STORAGE/$base" 
-
-if [ -f "$file" ] && [ -s "$file" ]; then
-  BOOT="$file"
-  return 0
-fi
+iso "$STORAGE/$base" && return 0
 
 TMP="$STORAGE/${base%.*}.tmp"
 rm -f "$TMP"
@@ -62,6 +57,7 @@ if ((size<100000)); then
   error "Invalid ISO file: Size is smaller than 100 KB" && exit 62
 fi
 
-mv -f "$TMP" "$file"
+mv -f "$TMP" "$STORAGE/$base"
+! iso "$STORAGE/$base" && exit 63
 
 return 0