diff --git a/tools/run_tests/build_python.sh b/tools/run_tests/build_python.sh
index 13d745d14fef1cf6b0c7574907e0a0462662a40e..f0c15a3ee4910f3a4d473a6d8ade3886f5110581 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.