diff --git a/2.6-rc/alpine3.7/Dockerfile b/2.6-rc/alpine3.7/Dockerfile
index f3976adb0..d053901a5 100644
--- a/2.6-rc/alpine3.7/Dockerfile
+++ b/2.6-rc/alpine3.7/Dockerfile
@@ -11,7 +11,7 @@ ENV RUBY_MAJOR 2.6-rc
 ENV RUBY_VERSION 2.6.0-preview2
 ENV RUBY_DOWNLOAD_SHA256 00ddfb5e33dee24469dd0b203597f7ecee66522ebb496f620f5815372ea2d3ec
 ENV RUBYGEMS_VERSION 2.7.7
-ENV BUNDLER_VERSION 1.16.3
+ENV BUNDLER_VERSION 1.16.4
 
 # some of ruby's build scripts are written in ruby
 #   we purge system ruby later to make sure our final image uses what we just built
diff --git a/2.6-rc/stretch/Dockerfile b/2.6-rc/stretch/Dockerfile
index e5d7d6910..9d049df98 100644
--- a/2.6-rc/stretch/Dockerfile
+++ b/2.6-rc/stretch/Dockerfile
@@ -11,7 +11,7 @@ ENV RUBY_MAJOR 2.6-rc
 ENV RUBY_VERSION 2.6.0-preview2
 ENV RUBY_DOWNLOAD_SHA256 00ddfb5e33dee24469dd0b203597f7ecee66522ebb496f620f5815372ea2d3ec
 ENV RUBYGEMS_VERSION 2.7.7
-ENV BUNDLER_VERSION 1.16.3
+ENV BUNDLER_VERSION 1.16.4
 
 # some of ruby's build scripts are written in ruby
 #   we purge system ruby later to make sure our final image uses what we just built
diff --git a/2.6-rc/stretch/slim/Dockerfile b/2.6-rc/stretch/slim/Dockerfile
index f36b73851..ee564e084 100644
--- a/2.6-rc/stretch/slim/Dockerfile
+++ b/2.6-rc/stretch/slim/Dockerfile
@@ -23,7 +23,7 @@ ENV RUBY_MAJOR 2.6-rc
 ENV RUBY_VERSION 2.6.0-preview2
 ENV RUBY_DOWNLOAD_SHA256 00ddfb5e33dee24469dd0b203597f7ecee66522ebb496f620f5815372ea2d3ec
 ENV RUBYGEMS_VERSION 2.7.7
-ENV BUNDLER_VERSION 1.16.3
+ENV BUNDLER_VERSION 1.16.4
 
 # some of ruby's build scripts are written in ruby
 #   we purge system ruby later to make sure our final image uses what we just built