diff --git a/tools/dockerfile/interoptest/grpc_interop_python/build_interop.sh b/tools/dockerfile/interoptest/grpc_interop_python/build_interop.sh
index 468aa20e3fd..e66a6a3f496 100755
--- a/tools/dockerfile/interoptest/grpc_interop_python/build_interop.sh
+++ b/tools/dockerfile/interoptest/grpc_interop_python/build_interop.sh
@@ -28,5 +28,7 @@ cp -r /var/local/jenkins/service_account $HOME || true
 
 cd /var/local/git/grpc
 
+python3.7 -m pip install six
+
 # interop tests only run using python3.7 currently (and python build is slow)
 tools/run_tests/run_tests.py -l python --compiler python3.7 -c opt --build_only