diff --git a/Project.toml b/Project.toml
index 8c170bb7..e76570b7 100644
--- a/Project.toml
+++ b/Project.toml
@@ -29,7 +29,7 @@ ForwardDiff = "0.10"
 IterativeSolvers = "0.9"
 LinearMaps = "3"
 OrdinaryDiffEq = "5, 6"
-QuantumOpticsBase = "0.3"
+QuantumOpticsBase = "0.3, 0.4"
 RecursiveArrayTools = "2"
 Reexport = "0.2, 1.0"
 StochasticDiffEq = "6"