diff --git a/.changes/unreleased/Under the Hood-20240221-104344.yaml b/.changes/unreleased/Under the Hood-20240221-104344.yaml
new file mode 100644
index 00000000..bd1423a9
--- /dev/null
+++ b/.changes/unreleased/Under the Hood-20240221-104344.yaml	
@@ -0,0 +1,6 @@
+kind: Under the Hood
+body: Restrict protobuf library to major version 4.
+time: 2024-02-21T10:43:44.642458-05:00
+custom:
+  Author: peterallenwebb
+  Issue: "9566"
diff --git a/pyproject.toml b/pyproject.toml
index 03e046d6..10104d46 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,7 +34,7 @@ dependencies = [
   "Jinja2~=3.0",
   "mashumaro[msgpack]~=3.9",
   "pathspec>=0.9,<0.12",
-  "protobuf>=4.0.0",
+  "protobuf>=4.0.0,<5.0.0",
   "python-dateutil~=2.0",
   "requests<3.0.0",
   "typing-extensions~=4.4",