diff --git a/spacy/cli/train.py b/spacy/cli/train.py
index 58c30baf2..896868419 100644
--- a/spacy/cli/train.py
+++ b/spacy/cli/train.py
@@ -16,7 +16,7 @@ from .. import util
 def train(language, output_dir, train_data, dev_data, n_iter, tagger, parser, ner):
     output_path = Path(output_dir)
     train_path = Path(train_data)
-    dev_path = Path(dev_data)
+    dev_path = Path(dev_data) if dev_data else None
     check_dirs(output_path, data_path, dev_path)
 
     lang = util.get_lang_class(language)
@@ -26,12 +26,13 @@ def train(language, output_dir, train_data, dev_data, n_iter, tagger, parser, ne
     parser_cfg['features'] = lang.Defaults.parser_features
     entity_cfg['features'] = lang.Defaults.entity_features
     gold_train = list(read_gold_json(train_path))
-    gold_dev = list(read_gold_json(dev_path))
+    gold_dev = list(read_gold_json(dev_path)) if dev_path else None
 
     train_model(lang, gold_train, gold_dev, output_path, tagger_cfg, parser_cfg,
                 entity_cfg, n_iter)
-    scorer = evaluate(lang, list(read_gold_json(dev_loc)), output_path)
-    print_results(scorer)
+    if gold_dev:
+        scorer = evaluate(lang, gold_dev, output_path)
+        print_results(scorer)
 
 
 def train_config(config):
@@ -54,7 +55,7 @@ def train_model(Language, train_data, dev_data, output_path, tagger_cfg, parser_
         for itn, epoch in enumerate(trainer.epochs(n_iter, augment_data=None)):
             for doc, gold in epoch:
                 trainer.update(doc, gold)
-            dev_scores = trainer.evaluate(dev_data)
+            dev_scores = trainer.evaluate(dev_data) if dev_data else []
             print_progress(itn, trainer.nlp.parser.model.nr_weight,
                            trainer.nlp.parser.model.nr_active_feat,
                            **dev_scores.scores)
@@ -82,8 +83,10 @@ def evaluate(Language, gold_tuples, output_path):
 def check_dirs(input_path, train_path, dev_path):
     if not output_path.exists():
         util.sys_exit(output_path.as_posix(), title="Output directory not found")
-    if not train_path.exists() and train_path.is_file():
+    if not train_path.exists() or not train_path.is_file():
         util.sys_exit(train_path.as_posix(), title="Training data not found")
+    if dev_path and not dev_path.exists():
+        util.sys_exit(dev_path.as_posix(), title="Development data not found")
 
 
 def print_progress(itn, nr_weight, nr_active_feat, **scores):