diff --git a/src/script/api/script_object.cpp b/src/script/api/script_object.cpp
index d9aefca3cf..679efd1a7c 100644
--- a/src/script/api/script_object.cpp
+++ b/src/script/api/script_object.cpp
@@ -290,7 +290,7 @@ ScriptObject::ActiveInstance::~ActiveInstance()
 	if (!StrEmpty(text) && (GetCommandFlags(cmd) & CMD_STR_CTRL) == 0) {
 		/* The string must be valid, i.e. not contain special codes. Since some
 		 * can be made with GSText, make sure the control codes are removed. */
-		str_validate(text, text + strlen(text)), SVS_NONE);
+		::str_validate(const_cast<char *>(text), text + strlen(text), SVS_NONE);
 	}
 
 	/* Set the default callback to return a true/false result of the DoCommand */