diff --git a/MyCapytain/resources/texts/local/capitains/cts.py b/MyCapytain/resources/texts/local/capitains/cts.py
index 786f6812..ef01fc86 100644
--- a/MyCapytain/resources/texts/local/capitains/cts.py
+++ b/MyCapytain/resources/texts/local/capitains/cts.py
@@ -659,7 +659,7 @@ def siblingsId(self) -> Tuple[CtsReference, CtsReference]:
         if start + 1 == len(document_references) or end + 1 == len(document_references):
             # If the passage is already at the end
             _next = None
-        elif end + range_length > len(document_references):
+        elif end + range_length >= len(document_references):
             if start == end:
                 _next = document_references[-1]
             else:
diff --git a/tests/resources/texts/local/commonTests.py b/tests/resources/texts/local/commonTests.py
index 5932e0f6..78dbb817 100644
--- a/tests/resources/texts/local/commonTests.py
+++ b/tests/resources/texts/local/commonTests.py
@@ -716,6 +716,10 @@ def test_siblingsId(self, simple):
             self.assertEqual(("1-4", "9-12"), (str(p), str(n)), "Middle node should have right siblings")
             p, n = self.FULL_EPIGRAMMATA.getTextualNode(CtsReference("5-10"), simple=simple).siblingsId
             self.assertEqual(("1-4", "11-14"), (str(p), str(n)), "Middle node should have right siblings")
+            # This test makes sure that siblingsId functions when end + range_length == len(document_references)
+            # Previously when this was the case siblingsId would throw an IndexError
+            p, n = self.FULL_EPIGRAMMATA.getTextualNode(CtsReference("2-8"), simple=simple).siblingsId
+            self.assertEqual(("1-1", "9-14"), (str(p), str(n)), "Middle node should have right siblings")
             # NONE !
             p, n = self.FULL_EPIGRAMMATA.getTextualNode(CtsReference("1-14"), simple=simple).siblingsId
             self.assertEqual((None, None), (p, n), "If whole range, nothing !")