diff --git a/.changes/unreleased/Dependencies-20240222-102947.yaml b/.changes/unreleased/Dependencies-20240222-102947.yaml
new file mode 100644
index 00000000000..9c21d51e21e
--- /dev/null
+++ b/.changes/unreleased/Dependencies-20240222-102947.yaml
@@ -0,0 +1,6 @@
+kind: Dependencies
+body: Restrict protobuf to 4.* versions
+time: 2024-02-22T10:29:47.595435-08:00
+custom:
+  Author: QMalcolm
+  PR: "9566"
diff --git a/core/setup.py b/core/setup.py
index 08fe234a8a8..e718448ecd7 100644
--- a/core/setup.py
+++ b/core/setup.py
@@ -79,7 +79,7 @@
         # ----
         # Expect compatibility with all new versions of these packages, so lower bounds only.
         "packaging>20.9",
-        "protobuf>=4.0.0",
+        "protobuf>=4.0.0,<5",
         "pytz>=2015.7",
         "pyyaml>=6.0",
         "typing-extensions>=3.7.4",