diff --git a/qurator/dinglehopper/cli.py b/qurator/dinglehopper/cli.py
index 9a2a837..c9b347f 100644
--- a/qurator/dinglehopper/cli.py
+++ b/qurator/dinglehopper/cli.py
@@ -1,3 +1,4 @@
+import json
 import os
 
 import click
@@ -55,7 +56,10 @@ def gen_diff_report(gt_in, ocr_in, css_prefix, joiner, none, matches=None):
         pos = 0
         for ocr_line in ocr_lines_sorted:
             if ocr_line.line not in ocr_line_region_id.keys():
-                ocr_line_region_id[ocr_line.line] = ocr_in.segment_id_for_pos(pos)
+                try:
+                    ocr_line_region_id[ocr_line.line] = ocr_in.segment_id_for_pos(pos)
+                except AssertionError:
+                    pass
             pos += ocr_line.length
 
         ocr_ids = {None: None}
@@ -159,6 +163,7 @@ def process(gt, ocr, report_prefix, *, metrics="cer,wer", textequiv_level="regio
         )
     )
     env.filters["json_float"] = json_float
+    env.filters["json_dumps"] = json.dumps
 
     for report_suffix in (".html", ".json"):
         template_fn = "report" + report_suffix + ".j2"
diff --git a/qurator/dinglehopper/templates/report.json.j2 b/qurator/dinglehopper/templates/report.json.j2
index 161d342..a632590 100644
--- a/qurator/dinglehopper/templates/report.json.j2
+++ b/qurator/dinglehopper/templates/report.json.j2
@@ -6,6 +6,6 @@
     {% if n_characters is not none %}"n_characters": {{ n_characters }},{% endif %}
     {% if n_words is not none %}"n_words": {{ n_words }},{% endif %}
 {% endif %}
-    "gt": "{{ gt }}",
-    "ocr": "{{ ocr }}"
+    "gt": {{ gt|json_dumps }},
+    "ocr": {{ ocr|json_dumps }}
 }