diff --git a/pyproject.toml b/pyproject.toml
index 1cbfffc3a..4b08f5830 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -68,6 +68,7 @@ server = [
     "fastapi>=0.103.1",
     "pyyaml~=6.0",
     "optimade[mongo]",
+    "numpy>=1.20"
 ]
 
 # Client minded
diff --git a/requirements-server.txt b/requirements-server.txt
index 04f5dc957..7ac9463e2 100644
--- a/requirements-server.txt
+++ b/requirements-server.txt
@@ -2,4 +2,5 @@ elasticsearch==7.17.7
 elasticsearch-dsl==7.4.0
 fastapi==0.103.1
 mongomock==4.1.2
+numpy>=1.20
 pymongo==4.5.0