Correct.

You MUST EXPLICITLY invoke your fifth amendment right against self-incrimination.

(Okay, there may be some edge cases where invoking the fifth is implied, but SCOTUS has merely acknowledged that these edge cases could exist, but to my knowledge has never given rules for when it applies. Better safe than sorry.)

e: see Salinas v Texas[0] for example

[0] https://www.law.cornell.edu/supremecourt/text/12-246#writing...