diff --git a/requirements.txt b/requirements.txt
index f1ece8ea..868448fe 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -22,6 +22,6 @@ pyparsing>=2.0.2,<4
 requests
 rlp>=3,<5
 semantic_version
-z3-solver<=4.13.0.0,>=4.8.8.0
+z3-solver>=4.8.8.0,<=4.13.3.0
 matplotlib
 certifi>=2020.06.20