diff --git a/owlbot-postprocessor/Dockerfile b/owlbot-postprocessor/Dockerfile
index 539940a..9ccba19 100644
--- a/owlbot-postprocessor/Dockerfile
+++ b/owlbot-postprocessor/Dockerfile
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM ruby:3.3-bookworm
+FROM ruby:3.3.5-bookworm
 RUN apt-get update \
     && apt-get -y upgrade \
     && apt-get -y autoremove \