diff --git a/Dockerfile.updater-core b/Dockerfile.updater-core
index de950c6968..b643af9f70 100644
--- a/Dockerfile.updater-core
+++ b/Dockerfile.updater-core
@@ -110,10 +110,10 @@ RUN for ecosystem in git_submodules terraform github_actions hex elm docker nuge
 
 WORKDIR $DEPENDABOT_HOME/dependabot-updater
 
-# When bumping Bundler, need to also regenerate `updater/Gemfile.lock` via `bundle lock --update --bundler`
-# Generally simplest to match the bundler version to the one that comes by default with whatever Ruby version we install.
-# This way other projects that import this library don't have to futz around with installing new / unexpected bundler versions.
-ARG BUNDLER_V2_VERSION=2.5.3
+# When bumping Bundler, need to also:
+# * Regenerate `updater/Gemfile.lock` via `BUNDLE_GEMFILE=updater/Gemfile bundle lock --update --bundler`
+# * Regenerate `Gemfile.lock` via `bundle lock --update --bundler`.
+ARG BUNDLER_V2_VERSION=2.5.5
 
 RUN gem install bundler -v $BUNDLER_V2_VERSION --no-document && \
  rm -rf /var/lib/gems/*/cache/* && \
diff --git a/Gemfile.lock b/Gemfile.lock
index 1c045acf33..aabb4a08ac 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -387,4 +387,4 @@ DEPENDENCIES
   webrick (>= 1.7)
 
 BUNDLED WITH
-   2.5.3
+   2.5.5
diff --git a/updater/Gemfile.lock b/updater/Gemfile.lock
index 747345337f..f643552f0d 100644
--- a/updater/Gemfile.lock
+++ b/updater/Gemfile.lock
@@ -405,4 +405,4 @@ DEPENDENCIES
   webrick (>= 1.7)
 
 BUNDLED WITH
-   2.5.3
+   2.5.5