Imam Hasan & Husayn praying behind Marwan

 “Narrated from Musa ibn Ja’far, from his father [al-Sadiq]: Al-Hasan and al-Husayn (peace be upon him) were praying behind Marwan ibn Al-Hakam, so they said to one of them: 

Did your father repeat his prayer when he returned home?

He said: No, by God, he did not add to his prayers.”

نوادر الراوندي : باسناده عن موسى بن جعفر، عن أبيه (ع) قال: كان الحسن والحسين (ع) يصليان خلف مروان بنالحكم فقالوا لأحدهما : ما كان ابوك يصلى إذا رجع إلى البيت ؟

فقال: لا والله ما كان يزيد على صلاته .

(Al-Taqiyya, by Shaykh al-Ansari page 45)

“Narrated from Abi Ja’far: 

Do not pray behind a nasibi or nor give them any honor, unless you fear for yourselves to be exposed and singled out. Pray in your homes first, then pray with them, and make your prayers with them voluntary.”

وعن أبي جعفر محمد بن علي عليه السلام قال: لا تصلوا خلف ناصب ولا كرامة، إلا أن تخافوا على أنفسكم أن تشهروا ويشار إليكم، فصلوافي بيوتكم ثم صلوا معهم، واجعلوا صلاتكم معهم تطوعا 

http://shiaonlinelibrary.com/الكتب/362_التقية-الشيخ-الأنصاري/الصفحة_45

Sayyid Borujerdi includes this narration in a set of narrations which permit taqiyya, and making one engaging in it exempted from repeating the prayer afterwards.

ودلالة هذه الروايات على أن جواز التقية واجزائها عن الإعادة والقضاء بعد

http://shiaonlinelibrary.com/الكتب/1093_القواعد-الفقهية-السيد-البجنوردي-ج-٥/الصفحة_66

Why? 

Because you will be praying a voluntary prayer, behind the nasibi (like Marwan) - out of taqiyya. Not your obligatory prayer. Thus, you do not need to repeat your prayer. 

Wa Allahu A’lam