diff --git a/src/script/squirrel.cpp b/src/script/squirrel.cpp
--- a/src/script/squirrel.cpp
+++ b/src/script/squirrel.cpp
@@ -448,7 +448,7 @@ bool Squirrel::CallStringMethodStrdup(HS
 	if (!this->CallMethod(instance, method_name, &ret, suspend)) return false;
 	if (ret._type != OT_STRING) return false;
 	*res = stredup(ObjectToString(&ret));
-	StrMakeValidInPlace(*res);
+	StrMakeValidInPlace(const_cast<char *>(*res));
 	return true;
 }