diff --git a/Project.toml b/Project.toml
index b2a968fa..690184c8 100644
--- a/Project.toml
+++ b/Project.toml
@@ -28,6 +28,7 @@ DiffEqCallbacks = "2"
 FFTW = "1"
 ForwardDiff = "0.10"
 IterativeSolvers = "0.9"
+KrylovKit = "0.6"
 LinearMaps = "3"
 OrdinaryDiffEq = "5, 6"
 QuantumOpticsBase = "0.3, 0.4"