diff --git a/docs/Project.toml b/docs/Project.toml
index 7408867..88fa759 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -28,6 +28,7 @@ DFTK = "0.7"
 Documenter = "~1.8, 1.16"
 EmpiricalPotentials = "0.2.5"
 GeometryOptimization = "0.1.5"
+OptimizationNLopt = "0.3.9"
 PseudoPotentialData = "0.2"
 Unitful = "1.28.0"
 UnitfulAtomic = "1.0.0"