diff --git a/pyproject.toml b/pyproject.toml
index 619d00e..62fdded 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,7 +33,7 @@ classifiers = [
     "Topic :: Internet :: WWW/HTTP",
 ]
 keywords = ["requests", "http", "caching", "web"]
-dependencies = ["requests >= 2.16.0", "msgpack >= 0.5.2"]
+dependencies = ["requests >= 2.16.0", "msgpack >= 0.5.2, < 2.0.0"]
 requires-python = ">=3.7"
 
 [project.urls]