diff --git a/.mci.yml b/.mci.yml
index 7f35da88d4..da502baef1 100644
--- a/.mci.yml
+++ b/.mci.yml
@@ -10,9 +10,10 @@ exec_timeout_secs: 3600
 variables:
 
     # If updating mongoc_version_minimum, also update:
-    # - the default value of --c-driver-build-ref in etc/make_release.py
     # - LIBBSON_REQUIRED_VERSION and LIBMONGOC_REQUIRED_VERSION in CMakeLists.txt
     # - the version of pkg:github/mongodb/mongo-c-driver in etc/purls.txt
+    # - the default value of --c-driver-build-ref in etc/make_release.py
+    # Only LIBMONGOC_DOWNLOAD_VERSION needs to be updated when pinning to an unreleased commit.
     mongoc_version_minimum: &mongoc_version_minimum "1.28.0"
 
     integration_matrix:
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1617b2d2a7..cbf0bedc0c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -54,7 +54,7 @@ set(LIBBSON_REQUIRED_ABI_VERSION 1.0)
 
 # Also update etc/purls.txt.
 set(LIBMONGOC_REQUIRED_VERSION 1.28.0)
-set(LIBMONGOC_DOWNLOAD_VERSION 1.28.0)
+set(LIBMONGOC_DOWNLOAD_VERSION d934cd5de55af65220816e4fd01ce3f9c0ef1cd4) # TODO: update to 1.29.0 once it is released.
 set(LIBMONGOC_REQUIRED_ABI_VERSION 1.0)
 
 set(NEED_DOWNLOAD_C_DRIVER false)