diff --git a/haystack/document_store/elasticsearch.py b/haystack/document_store/elasticsearch.py
index ca0cdb097..c9403342b 100644
--- a/haystack/document_store/elasticsearch.py
+++ b/haystack/document_store/elasticsearch.py
@@ -380,7 +380,7 @@ class ElasticsearchDocumentStore(BaseDocumentStore):
                     }
                 )
             body["query"]["bool"]["filter"] = filter_clause
-        result = scan(self.client, query=body, index=index)
+        result = list(scan(self.client, query=body, index=index))
 
         return result
 
diff --git a/requirements.txt b/requirements.txt
index 3f939efb8..8f2449277 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,7 +6,7 @@ gunicorn
 pandas
 sklearn
 psycopg2-binary; sys_platform != 'win32' and sys_platform != 'cygwin'
-elasticsearch
+elasticsearch>=7.7,<=7.10
 elastic-apm
 tox
 coverage
diff --git a/test/test_reader.py b/test/test_reader.py
index 5024a7a0e..819875773 100644
--- a/test/test_reader.py
+++ b/test/test_reader.py
@@ -28,7 +28,7 @@ def test_output(prediction):
 def test_no_answer_output(no_answer_prediction):
     assert no_answer_prediction is not None
     assert no_answer_prediction["question"] == "What is the meaning of life?"
-    assert math.isclose(no_answer_prediction["no_ans_gap"], -14.4729533, rel_tol=0.0001)
+    assert math.isclose(no_answer_prediction["no_ans_gap"], -13.048564434051514, rel_tol=0.0001)
     assert no_answer_prediction["answers"][0]["answer"] is None
     assert no_answer_prediction["answers"][0]["offset_start"] == 0
     assert no_answer_prediction["answers"][0]["offset_end"] == 0