diff --git a/Dockerfile b/Dockerfile
index 303b86b7..a68b373d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:2.7.1
+FROM ruby:2.7
 
 # throw errors if Gemfile has been modified since Gemfile.lock
 RUN bundle config --global frozen 1
diff --git a/Dockerfile-2.5 b/Dockerfile-2.5
index f453241e..f14decab 100644
--- a/Dockerfile-2.5
+++ b/Dockerfile-2.5
@@ -1,4 +1,4 @@
-FROM ruby:2.5.7
+FROM ruby:2.5
 
 # throw errors if Gemfile has been modified since Gemfile.lock
 RUN bundle config --global frozen 1
diff --git a/Dockerfile-2.6 b/Dockerfile-2.6
index 0bef7e0e..ee5f7de3 100644
--- a/Dockerfile-2.6
+++ b/Dockerfile-2.6
@@ -1,4 +1,4 @@
-FROM ruby:2.6.5
+FROM ruby:2.6
 
 # throw errors if Gemfile has been modified since Gemfile.lock
 RUN bundle config --global frozen 1
diff --git a/script/poll-for-db b/script/poll-for-db
index 97f1c794..f6877f34 100755
--- a/script/poll-for-db
+++ b/script/poll-for-db
@@ -4,7 +4,7 @@ appdir=$(cd $(dirname "$0")/.. && pwd)
 [ -f /etc/app-env ] || exec "$appdir/script/docker-environment" $0 $@
 
 for i in {1..60}; do
-  curl -sf db:3306 >/dev/null && exit
+  curl -sf telnet://db:3306 >/dev/null && exit
   sleep 1
 done