diff --git a/Dockerfile.ruby-2.1 b/Dockerfile.ruby-2.1
index 4cc26a0..75c55d6 100644
--- a/Dockerfile.ruby-2.1
+++ b/Dockerfile.ruby-2.1
@@ -1,6 +1,6 @@
 FROM ruby:2.1
 
-ENV PACKAGES "git-core" \
+ENV PACKAGES="git-core" \
 	LC_ALL=en_US.UTF-8
 
 ADD / /
diff --git a/Dockerfile.ruby-2.2 b/Dockerfile.ruby-2.2
index bba4ea2..3d1e2f1 100644
--- a/Dockerfile.ruby-2.2
+++ b/Dockerfile.ruby-2.2
@@ -1,6 +1,6 @@
 FROM ruby:2.2
 
-ENV PACKAGES "git-core" \
+ENV PACKAGES="git-core" \
 	LC_ALL=en_US.UTF-8
 
 ADD / /
diff --git a/Dockerfile.ruby-2.3 b/Dockerfile.ruby-2.3
index 514d916..79afc2f 100644
--- a/Dockerfile.ruby-2.3
+++ b/Dockerfile.ruby-2.3
@@ -1,6 +1,6 @@
 FROM ruby:2.3
 
-ENV PACKAGES "git-core" \
+ENV PACKAGES="git-core" \
 	LC_ALL=en_US.UTF-8
 
 ADD / /
diff --git a/Dockerfile.www-gitlab-com b/Dockerfile.www-gitlab-com
index 85b23b1..9be89f6 100644
--- a/Dockerfile.www-gitlab-com
+++ b/Dockerfile.www-gitlab-com
@@ -1,6 +1,6 @@
 FROM ruby:2.1
 
-ENV PACKAGES "git-core nodejs pandoc texlive-latex-recommended texlive-xetex texlive-fonts-recommended ed" \
+ENV PACKAGES="git-core nodejs pandoc texlive-latex-recommended texlive-xetex texlive-fonts-recommended ed" \
 	LC_ALL=en_US.UTF-8
 
 ADD / /