diff --git a/pyproject.toml b/pyproject.toml
index 995652be..1907f34e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,7 +36,7 @@ dependencies = [
   "requests",
   "rich ~= 13.0",
   "rfc8785 ~= 0.1.2",
-  "rfc3161-client ~= 0.1.2",
+  "rfc3161-client >= 0.1.2,< 1.1.0",
   # NOTE(ww): Both under active development, so strictly pinned.
   "sigstore-protobuf-specs == 0.3.2",
   "sigstore-rekor-types == 0.0.18",