Past participle + infinitive (fait, laissé, vu, entendu)
Summary
When a past participle is directly followed by an infinitive, the ordinary agreement rules bend: fait never agrees, laissé is now treated as invariable too, and verbs of perception agree only if the preceding object performs the infinitive's action.
Explanation
This rule is a special case that layers on top of ordinary past-participle agreement with avoir (see grammar.participle-agreement.avoir): when the participle is immediately followed by an infinitive, the usual test — does a direct object precede the verb? — is modified or overridden depending on which participle is involved.
Fait + infinitive is ALWAYS invariable, with no exceptions, regardless of what precedes it: elle s'est fait couper les cheveux (she had her hair cut), la maison qu'il a fait construire (the house he had built). This is a fixed, memorized exception; fait never agrees in this construction, even with a preceding direct object.
Laissé + infinitive used to follow the same logic as vu/entendu below, agreeing when the preceding object performed the infinitive's action (la femme qu'il a laissée partir, because the woman herself leaves). However, the 1990 spelling rectifications simplified this: laissé followed by an infinitive is now recommended to stay INVARIABLE in all cases, by analogy with fait: elle s'est laissé tomber, les enfants qu'il a laissé partir. Both the traditional agreeing form and the modern invariable form are attested; this library presents both but recommends the invariable modern rule as the safer, simpler choice.
Verbs of perception — vu, entendu, regardé, écouté, senti — followed by an infinitive keep the classic, more delicate rule: the participle agrees with a preceding direct object ONLY IF that object performs the action expressed by the infinitive. Compare la cantatrice que j'ai entendue chanter (I heard the singer sing — she is the one singing, so entendue agrees) with la chanson que j'ai entendu chanter (I heard the song sung — the song does not sing, someone else does, so entendu stays invariable).
This agree/don't-agree distinction with perception verbs comes down to a simple mental test: turn the preceding object into the subject of the infinitive and see if the sentence still makes sense. La cantatrice chante works, so agreement follows; la chanson chante does not really work (a song doesn't sing itself), so no agreement.
This construction connects closely to causative faire (faire + infinitive, see conjugation.causative-faire), which shares the same invariable-participle logic as fait here, and to ordinary participle agreement with avoir, which supplies the baseline rule that this construction modifies for fait, laissé, and the perception verbs.
Examples
Elle s'est fait couper les cheveux hier. — She had her hair cut yesterday. (fait + infinitive is always invariable.)
La maison qu'il a fait construire est magnifique. — The house he had built is magnificent. (fait stays invariable even with the preceding direct object que (= la maison).)
Elle s'est laissé tomber sur le canapé. — She let herself fall onto the sofa. (laissé + infinitive: recommended invariable form per the 1990 spelling rectifications.)
Les enfants qu'il a laissé partir sont rentrés tard. — The children he let leave came home late. (Modern invariable laissé; traditional usage would have agreed it as laissés.)
La cantatrice que j'ai entendue chanter avait une voix magnifique. — The singer I heard sing had a magnificent voice. (entendue agrees because la cantatrice performs the action of chanter.)
La chanson que j'ai entendu chanter à la radio m'a plu. — The song I heard sung on the radio pleased me. (entendu stays invariable because la chanson does not perform the action of chanter; someone else sings it.)
Common mistakes
La chanson que j'ai entendue chanter était belle.
La chanson que j'ai entendu chanter était belle.
With a past participle followed by an infinitive (entendre, voir, laisser faire...), the participle agrees with a preceding direct object only if that object performs the action of the infinitive. Here, la chanson does not sing — it is sung — so entendu stays invariable, not entendue.
Prerequisites
Related rules
past-participleagreementinfinitivecausative