The type of process variables are not be recognized by process

There is a process which contains a multiple subprocess. And when i define the process variable (e.g.: resultMap ) in subprocess scope and set the type to Object(java.util.Map), then when i use this variable in a script task (e.g.: resultMap.get("key")), it will report compile error. But when i move the variable definition out of the subprocess, and define it in the parent process scope, then i can use it normally.

Note: the script task is also inside the subprocess.