diff --git a/pyproject.toml b/pyproject.toml
index b4ba01a..3bfb18d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,7 +27,7 @@ homepage = "https://github.com/hobuinc/doppkit"
 repository = "https://github.com/hobuinc/doppkit"
 
 [project.optional-dependencies]
-GUI = ["qtpy", "PySide6-essentials", "qasync"]
+GUI = ["qtpy", "PySide6-essentials~=6.6.0", "qasync"]
 
 [tool.black]
 line-length = 88
diff --git a/src/doppkit/__init__.py b/src/doppkit/__init__.py
index d7cb459..6f2eaea 100644
--- a/src/doppkit/__init__.py
+++ b/src/doppkit/__init__.py
@@ -1,4 +1,4 @@
-__version__ = "0.4.1dev0"
+__version__ = "0.4.1"
 
 from . import cache
 from . import grid