diff --git a/Q/QuantumOpticsBase/Versions.toml b/Q/QuantumOpticsBase/Versions.toml
index 79573e0270d31ff..2b21c8f59caeebf 100644
--- a/Q/QuantumOpticsBase/Versions.toml
+++ b/Q/QuantumOpticsBase/Versions.toml
@@ -153,3 +153,6 @@ git-tree-sha1 = "2b031450a1b5a9e4f21036f518a27502e9410aeb"
 
 ["0.4.20"]
 git-tree-sha1 = "2d8635830edeacccd883630a1ebc8047f3b69b76"
+
+["0.4.21"]
+git-tree-sha1 = "abce3a922e9230a04f91c9f4f67cc7c53907621d"