diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index cac2c9a..4071767 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -23,6 +23,9 @@ jobs:
         with:
           ocaml-compiler: ${{ matrix.ocaml-compiler }}
 
+      - if: matrix.platform == 'macos-latest'
+        run: brew install gmp
+
       - name: Build mpfr from sources
         run: |
           wget --no-check-certificate https://www.mpfr.org/mpfr-4.2.1/mpfr-4.2.1.tar.gz