diff --git a/spacy/cli/converters/iob2json.py b/spacy/cli/converters/iob2json.py
index 4d456fa57..74bc22ada 100644
--- a/spacy/cli/converters/iob2json.py
+++ b/spacy/cli/converters/iob2json.py
@@ -12,17 +12,13 @@ def iob2json(input_path, output_path, n_sents=10, *a, **k):
     Convert IOB files into JSON format for use with train cli.
     """
     with input_path.open('r', encoding='utf8') as file_:
-        if n_sents:
-            lines = [' '.join(para) for para in partition_all(n_sents, file_)]
-        else:
-            lines = file_
-    sentences = read_iob(lines)
-
+        sentences = read_iob(file_)
+    docs = merge_sentences(sentences, n_sents)
     output_filename = input_path.parts[-1].replace(".iob", ".json")
     output_file = output_path / output_filename
     with output_file.open('w', encoding='utf-8') as f:
-        f.write(json_dumps(sentences))
-    prints("Created %d documents" % len(sentences),
+        f.write(json_dumps(docs))
+    prints("Created %d documents" % len(docs),
            title="Generated output file %s" % path2str(output_file))
 
 
@@ -46,3 +42,15 @@ def read_iob(raw_sents):
     paragraphs = [{'sentences': [sent]} for sent in sentences]
     docs = [{'id': 0, 'paragraphs': [para]} for para in paragraphs]
     return docs
+
+def merge_sentences(docs, n_sents):
+    counter = 0
+    merged = []
+    for group in partition_all(n_sents, docs):
+        group = list(group)
+        first = group.pop(0)
+        to_extend = first['paragraphs'][0]['sentences']
+        for sent in group[1:]:
+            to_extend.extend(sent['paragraphs'][0]['sentences'])
+        merged.append(first)
+    return merged