diff --git a/tools/migrate-main-instance.sh b/tools/migrate-main-instance.sh
index 79cdfd6..4d32a84 100755
--- a/tools/migrate-main-instance.sh
+++ b/tools/migrate-main-instance.sh
@@ -3,7 +3,7 @@
 configfile="$1"
 instancefile="$2"
 
-if grep "^arkserverroot=" <"$configfile" >/dev/null 2>&1 && [ ! -f "$instancefile" ]; then
+if ! grep '^arkSingleInstance=' <"$configfile" >/dev/null 2>&1 && grep "^arkserverroot=" <"$configfile" >/dev/null 2>&1 && [ ! -f "$instancefile" ]; then
   sed -n '/^#*\(ark\(\|flag\|opt\)_[^=]*\|arkserverroot\|serverMap\(\|ModId\)\)=/p' <"$configfile" >"$instancefile"
   sed -i '/^ark\(serverroot\|_\(RCONPort\|Port\|QueryPort\)\)=/d' "$configfile"
   echo 'defaultinstance="main"' >>"$configfile"