Short answer. Yes. Article 906 of the Civil Code gives any compulsory heir left less than their legitime, by any title, the right to demand that it be fully satisfied. The shortfall does not stand simply because it appears in a validly executed will; the heir can still insist on receiving the reserved share in full.
What the law says
Any compulsory heir to whom the testator has left by any title less than the legitime belonging to him may demand that the same be fully satisfied.
Civil Code, Article 906 — Completion Of Deficient Legitime. Read the full provision →
The legitime is a floor the will cannot go below
Article 906 protects compulsory heirs against exactly this scenario: any compulsory heir to whom the testator has left by any title less than the legitime belonging to him may demand that the same be fully satisfied. The legitime is treated as a reserved minimum, not a starting point the testator is free to reduce. A will that assigns a compulsory heir less than that reserved share does not simply stand as written on that point — the shortchanged heir has an affirmative right to demand the difference.
"By any title" covers more than an outright bequest
The article's phrase left by any title less than the legitime is deliberately broad. It is not limited to a direct cash or property bequest falling short — it reaches whatever form the testator used to leave something to the heir, whether as an inheritance, a legacy, or some other disposition, so long as the total value received by that heir under the will comes up short of the legitime. The form of the gift does not shield a shortfall from this article.
The remedy is completion, not automatic invalidity
Article 906 does not say the will becomes void, or that the whole document is thrown out, because one heir received less than their share. The remedy it grants is narrower and more targeted: the heir may demand that the same be fully satisfied — meaning the shortfall is made up so the legitime is completed, while the rest of the will's dispositions are not automatically disturbed by this article alone.
What you need to work out your own shortfall
Acting on this right starts with knowing two figures: what your legitime actually amounts to under the rules governing compulsory heirs, and what the will actually left you, valued fairly. Gather the will itself, an accounting of the estate's assets, and anything showing what you were assigned, since Article 906 gives you the right to demand completion only once the gap between those two figures is established. This right belongs to the compulsory heir personally; the article does not extend it to a creditor of that heir or to anyone else claiming through them.