diff --git a/odoo/addons/base/models/ir_actions_report.py b/odoo/addons/base/models/ir_actions_report.py
index 934a229cb13..594af972ff0 100644
--- a/odoo/addons/base/models/ir_actions_report.py
+++ b/odoo/addons/base/models/ir_actions_report.py
@@ -717,18 +717,18 @@ class IrActionsReport(models.Model):
 
             # Split the pdf for each record using the PDF outlines.
 
-            if not self.attachment:
-                # Splitting the pdf is not needed since we don't have any attachment to generate.
-                collected_streams[False] = {'stream': pdf_content_stream}
-            elif len(res_ids_wo_stream) == 1:
-                # Only one record: append the whole PDF.
+            # Only one record: append the whole PDF.
+            if len(res_ids_wo_stream) == 1:
                 collected_streams[res_ids_wo_stream[0]]['stream'] = pdf_content_stream
-            else:
-                # In case of multiple docs, we need to split the pdf according the records.
-                # To do so, we split the pdf based on top outlines computed by wkhtmltopdf.
-                # An outline is a <h?> html tag found on the document. To retrieve this table,
-                # we look on the pdf structure using pypdf to compute the outlines_pages from
-                # the top level heading in /Outlines.
+                return collected_streams
+
+            # In case of multiple docs, we need to split the pdf according the records.
+            # To do so, we split the pdf based on top outlines computed by wkhtmltopdf.
+            # An outline is a <h?> html tag found on the document. To retrieve this table,
+            # we look on the pdf structure using pypdf to compute the outlines_pages from
+            # the top level heading in /Outlines.
+            html_ids_wo_none = [x for x in html_ids if x]
+            if len(res_ids_wo_stream) > 1 and set(res_ids_wo_stream) == set(html_ids_wo_none):
                 reader = PdfFileReader(pdf_content_stream)
                 root = reader.trailer['/Root']
                 has_valid_outlines = '/Outlines' in root and '/First' in root['/Outlines']
@@ -747,18 +747,27 @@ class IrActionsReport(models.Model):
                         break
                     node = node['/Next']
                 outlines_pages = sorted(set(outlines_pages))
-                # There should be only one top-level heading by document
-                assert len(outlines_pages) == len(res_ids)
+
+                # The number of outlines must be equal to the number of records to be able to split the document.
+                has_same_number_of_outlines = len(outlines_pages) == len(res_ids)
+
                 # There should be a top-level heading on first page
-                assert outlines_pages[0] == 0
-                for i, num in enumerate(outlines_pages):
-                    to = outlines_pages[i + 1] if i + 1 < len(outlines_pages) else reader.numPages
-                    attachment_writer = PdfFileWriter()
-                    for j in range(num, to):
-                        attachment_writer.addPage(reader.getPage(j))
-                    stream = io.BytesIO()
-                    attachment_writer.write(stream)
-                    collected_streams[res_ids[i]]['stream'] = stream
+                has_top_level_heading = outlines_pages[0] == 0
+
+                if has_same_number_of_outlines and has_top_level_heading:
+                    # Split the PDF according to outlines.
+                    for i, num in enumerate(outlines_pages):
+                        to = outlines_pages[i + 1] if i + 1 < len(outlines_pages) else reader.numPages
+                        attachment_writer = PdfFileWriter()
+                        for j in range(num, to):
+                            attachment_writer.addPage(reader.getPage(j))
+                        stream = io.BytesIO()
+                        attachment_writer.write(stream)
+                        collected_streams[res_ids[i]]['stream'] = stream
+
+                    return collected_streams
+
+            collected_streams[False] = {'stream': pdf_content_stream}
 
         return collected_streams