diff --git a/setup.py b/setup.py
index 77b43f1..631d151 100755
--- a/setup.py
+++ b/setup.py
@@ -62,7 +62,7 @@ setup(
     extras_require={
 
         # serialization
-        'msgspec': ["msgspec >= 0.3.2'; python_version >= '3.9'"],
+        'msgspec': ['msgspec >= "0.4.0"'],
 
     },
     tests_require=['pytest'],