diff --git a/pyproject.toml b/pyproject.toml
index 1b2a577eba..8b54e7f12f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -73,7 +73,7 @@ dependencies = [
   "Pillow",
 
   # OpenAI tokenizer
-  "tiktoken>=0.3.2",
+  "tiktoken>=0.3.2,<0.5.0",
 
   # Schema validation
   "jsonschema",