diff --git a/deepspeed/pt/deepspeed_config.py b/deepspeed/pt/deepspeed_config.py
old mode 100644
new mode 100755
index b520d322bd5e..460c72399c6b
--- a/deepspeed/pt/deepspeed_config.py
+++ b/deepspeed/pt/deepspeed_config.py
@@ -256,7 +256,8 @@ def _initialize_params(self, param_dict):
         self.dynamic_loss_scale_args = get_dynamic_loss_scale_args(param_dict)
 
         self.optimizer_name = get_optimizer_name(param_dict)
-        if self.optimizer_name.lower() in DEEPSPEED_OPTIMIZERS:
+        if self.optimizer_name is not None and \
+            self.optimizer_name.lower() in DEEPSPEED_OPTIMIZERS:
             self.optimizer_name = self.optimizer_name.lower()
 
         self.optimizer_params = get_optimizer_params(param_dict)
diff --git a/tests/unit/test_ds_config.py b/tests/unit/test_ds_config.py
new file mode 100755
index 000000000000..8e49748710c2
--- /dev/null
+++ b/tests/unit/test_ds_config.py
@@ -0,0 +1,19 @@
+import pytest
+import os
+import json
+from deepspeed.pt import deepspeed_config as ds_config
+
+
+def test_only_required_fields(tmpdir):
+    '''Ensure that config containing only the required fields is accepted. '''
+    cfg_json = tmpdir.mkdir('ds_config_unit_test').join('minimal.json')
+
+    with open(cfg_json, 'w') as f:
+        required_fields = {'train_batch_size': 64}
+        json.dump(required_fields, f)
+
+    run_cfg = ds_config.DeepSpeedConfig(cfg_json)
+    assert run_cfg is not None
+    assert run_cfg.train_batch_size == 64
+    assert run_cfg.train_micro_batch_size_per_gpu == 64
+    assert run_cfg.gradient_accumulation_steps == 1