diff --git a/src/python/src/grpc/_adapter/_c/utility.c b/src/python/src/grpc/_adapter/_c/utility.c
index 64b3428f2b1..97f2f35b8eb 100644
--- a/src/python/src/grpc/_adapter/_c/utility.c
+++ b/src/python/src/grpc/_adapter/_c/utility.c
@@ -196,10 +196,11 @@ int pygrpc_produce_op(PyObject *op, grpc_op *result) {
       return 0;
     }
     if (!PyTuple_Check(PyTuple_GET_ITEM(op, STATUS_INDEX))) {
-      char buf[64];
-      snprintf(buf, sizeof(buf), "expected tuple status in op of length %d",
-               STATUS_TUPLE_SIZE);
-      PyErr_SetString(PyExc_TypeError, buf);
+      char *buf;
+      gpr_asprintf(&buf, "expected tuple status in op of length %d",
+                   STATUS_TUPLE_SIZE);
+      PyErr_SetString(PyExc_ValueError, buf);
+      gpr_free(buf);
       return 0;
     }
     c_op.data.send_status_from_server.status = PyInt_AsLong(
diff --git a/tools/run_tests/build_python.sh b/tools/run_tests/build_python.sh
index 53db6af0ea1..d9b7644f449 100755
--- a/tools/run_tests/build_python.sh
+++ b/tools/run_tests/build_python.sh
@@ -38,5 +38,5 @@ rm -rf python2.7_virtual_environment
 virtualenv -p /usr/bin/python2.7 python2.7_virtual_environment
 source python2.7_virtual_environment/bin/activate
 pip install -r src/python/requirements.txt
-CFLAGS="-I$root/include -std=c89" LDFLAGS=-L$root/libs/$CONFIG pip install src/python/src
+CFLAGS="-I$root/include -std=c89 -Werror" LDFLAGS=-L$root/libs/$CONFIG pip install src/python/src
 pip install src/python/interop