diff --git a/tools/run_tests/build_python.sh b/tools/run_tests/build_python.sh
index c4b5d98a53b298831e50d6d6b22199a308a96918..cb3446fc56594908192b48d63355db74036d79a3 100755
--- a/tools/run_tests/build_python.sh
+++ b/tools/run_tests/build_python.sh
@@ -111,6 +111,7 @@ TOOLCHAIN=${4:-$(toolchain)}
 ROOT=`pwd`
 export CFLAGS="-I$ROOT/include -std=gnu99 -fno-wrapv $CFLAGS"
 export GRPC_PYTHON_BUILD_WITH_CYTHON=1
+export LANG=en_US.UTF-8
 
 # Default python on the host to fall back to when instantiating e.g. the
 # virtualenv.