diff --git a/setup.py b/setup.py
index b1b2653c..a6bb988e 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,7 @@
     keywords="dataclasses json",
     install_requires=[
         "dataclasses;python_version=='3.6'",
-        "marshmallow==3.0.0b18"
+        "marshmallow>=3.0.0b20"
     ],
     python_requires=">=3.6",
     extras_require={