diff --git a/tools/dockerfile/interoptest/grpc_interop_ruby/Dockerfile b/tools/dockerfile/interoptest/grpc_interop_ruby/Dockerfile
index 88b5130..7ae9f7d 100644
--- a/tools/dockerfile/interoptest/grpc_interop_ruby/Dockerfile
+++ b/tools/dockerfile/interoptest/grpc_interop_ruby/Dockerfile
@@ -70,12 +70,12 @@ RUN apt-get update && apt-get install -y time && apt-get clean
 RUN gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
 RUN \curl -sSL https://get.rvm.io | bash -s stable
 
-# Install Ruby 2.1
-RUN /bin/bash -l -c "rvm install ruby-2.1"
-RUN /bin/bash -l -c "rvm use --default ruby-2.1"
+# Install Ruby 2.1.8
+RUN /bin/bash -l -c "rvm install ruby-2.1.8"
+RUN /bin/bash -l -c "rvm use --default ruby-2.1.8"
 RUN /bin/bash -l -c "echo 'gem: --no-ri --no-rdoc' > ~/.gemrc"
 RUN /bin/bash -l -c "echo 'export PATH=/usr/local/rvm/bin:$PATH' >> ~/.bashrc"
-RUN /bin/bash -l -c "echo 'rvm --default use ruby-2.1' >> ~/.bashrc"
+RUN /bin/bash -l -c "echo 'rvm --default use ruby-2.1.8' >> ~/.bashrc"
 RUN /bin/bash -l -c "gem install bundler --no-ri --no-rdoc"
 
 # Prepare ccache
diff --git a/tools/dockerfile/interoptest/grpc_interop_ruby/build_interop.sh b/tools/dockerfile/interoptest/grpc_interop_ruby/build_interop.sh
index 97b3860..cec046d 100755
--- a/tools/dockerfile/interoptest/grpc_interop_ruby/build_interop.sh
+++ b/tools/dockerfile/interoptest/grpc_interop_ruby/build_interop.sh
@@ -38,7 +38,7 @@ git clone --recursive /var/local/jenkins/grpc /var/local/git/grpc
 cp -r /var/local/jenkins/service_account $HOME || true
 
 cd /var/local/git/grpc
-rvm --default use ruby-2.1
+rvm --default use ruby-2.1.8
 
 # build Ruby interop client and server
 (cd src/ruby && gem update bundler && bundle && rake compile)