diff --git a/datawrapper/__main__.py b/datawrapper/__main__.py
index 296d1dd..5d2a3a4 100644
--- a/datawrapper/__main__.py
+++ b/datawrapper/__main__.py
@@ -654,7 +654,7 @@ def create_chart(
         assert isinstance(obj, dict)
 
         # Add data, if provided
-        if data:
+        if data is not None:
             self.add_data(chart_id=obj["id"], data=data)
 
         # Return the result
@@ -734,7 +734,7 @@ def update_chart(
             _query["metadata"] = metadata
 
         # If there's nothing there to update, raise an exception
-        if not _query and not data:
+        if not _query and data is None:
             msg = "No updates submitted."
             logger.error(msg)
             raise InvalidRequest(msg)
@@ -1005,7 +1005,7 @@ def export_chart(
             "transparent": transparent,
         }
 
-        response = self.get(
+        content = self.get(
             f"{self._CHARTS_URL}/{chart_id}/export/{output}", params=_query
         )
 
@@ -1015,7 +1015,7 @@ def export_chart(
 
         # Write the file to the file path
         with open(_filepath, "wb") as fh:
-            fh.write(response.content)
+            fh.write(content)
 
         # Display the image if requested
         if display:
@@ -1102,6 +1102,7 @@ def add_data(self, chart_id: str, data: pd.DataFrame | str) -> bool:
         return self.put(
             f"{self._CHARTS_URL}/{chart_id}/data",
             data=_data.encode("utf-8"),
+            extra_headers={"content-type": "text/csv"},
             dump_data=False,
         )
 
diff --git a/tests/test_users.py b/tests/test_users.py
index 86b6db0..1ced3b6 100644
--- a/tests/test_users.py
+++ b/tests/test_users.py
@@ -21,13 +21,11 @@ def test_get_user():
     assert user["id"] == my_id
 
     # Get recently edited and published charts
-    charts = dw.get_recently_edited_charts()
+    charts = dw.get_recently_edited_charts(user["id"])
     assert isinstance(charts, dict)
-    assert isinstance(charts["charts"], list)
 
-    charts = dw.get_recently_published_charts()
+    charts = dw.get_recently_published_charts(user["id"])
     assert isinstance(charts, dict)
-    assert isinstance(charts["charts"], list)
 
 
 def test_edit_user():