diff --git a/pyproject.toml b/pyproject.toml
index 8d3652a2f..71e523c7c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,5 +7,6 @@ requires = [
     "preshed>=3.0.2,<3.1.0",
     "murmurhash>=0.28.0,<1.1.0",
     "thinc==8.0.0a0",
+    "blis>=0.4.0,<0.5.0"
 ]
 build-backend = "setuptools.build_meta"