diff --git a/tools/dockerfile/grpc_ruby/Dockerfile b/tools/dockerfile/grpc_ruby/Dockerfile
index f01f81d5392a289680e574295496f16f09406356..c84548c88028924c1309d574035d6a06750e1e44 100644
--- a/tools/dockerfile/grpc_ruby/Dockerfile
+++ b/tools/dockerfile/grpc_ruby/Dockerfile
@@ -12,14 +12,8 @@ RUN touch /var/local/git/grpc/include/grpc/support/string.h
 # Build the C core.
 RUN make install_c -C /var/local/git/grpc
 
-# Install the grpc gem locally with its dependencies and build the extension
-RUN /bin/bash -l -c 'cd /var/local/git/grpc/src/ruby && bundle && rake compile:grpc && gem build grpc.gemspec && gem install grpc'
-
-# TODO add a command to run the unittest tests when the bug below is fixed
-# - the tests fail due to an error in the C threading library:
-#   they fail with 'ruby: __pthread_mutex_cond_lock_adjust for unknown reasons' at the end of a testcase
-# - however, the interop server and client run OK, so this bug can be investigated
-# RUN /bin/bash -l -c 'cd /var/local/git/grpc/src/ruby && bundle && rake'
+# Build ruby gRPC and run its tests
+RUN /bin/bash -l -c 'cd /var/local/git/grpc/src/ruby && bundle && rake'
 
 # Add a cacerts directory containing the Google root pem file, allowing the ruby client to access the production test instance
 ADD cacerts cacerts