diff --git a/myst_parser/mocking.py b/myst_parser/mocking.py
index b65888e7..b59c747a 100644
--- a/myst_parser/mocking.py
+++ b/myst_parser/mocking.py
@@ -516,7 +516,12 @@ def run(self) -> list[nodes.Element]:
                 )
             self.renderer.nested_render_text(
                 file_content,
-                startline + 1,
+                # ``nested_render_text`` adds this to the 0-based token maps, and
+                # ``_render_tokens`` applies the 0-based to 1-based conversion
+                # afterwards. So the offset of the first included line is
+                # ``startline``, already 0-based; adding one here reported every
+                # line in the file one too low.
+                startline,
                 heading_offset=self.options.get("heading-offset", 0),
             )
         finally:
diff --git a/tests/test_renderers/fixtures/mock_include_errors.md b/tests/test_renderers/fixtures/mock_include_errors.md
index 6e443cb6..13820b8e 100644
--- a/tests/test_renderers/fixtures/mock_include_errors.md
+++ b/tests/test_renderers/fixtures/mock_include_errors.md
@@ -19,5 +19,48 @@ Error in include file:
 ```{include} bad.md
 ```
 .
-tmpdir/bad.md:2: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
+tmpdir/bad.md:1: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
+.
+
+Error line in include file:
+.
+```{include} bad_line3.md
+```
+.
+tmpdir/bad_line3.md:3: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
+.
+
+Error line in include file, after content in the parent:
+.
+para
+
+```{include} bad_line3.md
+```
+.
+tmpdir/bad_line3.md:3: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
+.
+
+Error line in include file with start-line:
+.
+```{include} bad_skipped.md
+:start-line: 2
+```
+.
+tmpdir/bad_skipped.md:4: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
+.
+
+Error line in include file with front matter:
+.
+```{include} bad_frontmatter.md
+```
+.
+tmpdir/bad_frontmatter.md:5: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
+.
+
+Error line in nested include file:
+.
+```{include} bad_outer.md
+```
+.
+tmpdir/bad_inner.md:3: (WARNING/2) Unknown interpreted text role "a". [myst.role_unknown]
 .
diff --git a/tests/test_renderers/test_include_directive.py b/tests/test_renderers/test_include_directive.py
index 9f03d633..d8501b04 100644
--- a/tests/test_renderers/test_include_directive.py
+++ b/tests/test_renderers/test_include_directive.py
@@ -41,6 +41,15 @@ def test_errors(file_params, tmp_path, monkeypatch):
     monkeypatch.chdir(tmp_path)
 
     tmp_path.joinpath("bad.md").write_text("{a}`b`")
+    # The role sits on line 3, so a warning reported against any other line is
+    # the include's own line attribution being off.
+    tmp_path.joinpath("bad_line3.md").write_text("line one\n\n{a}`b`\n")
+    tmp_path.joinpath("bad_skipped.md").write_text("skipped\nskipped2\n\n{a}`b`\n")
+    tmp_path.joinpath("bad_frontmatter.md").write_text("---\nx: 1\n---\n\n{a}`b`\n")
+    tmp_path.joinpath("bad_inner.md").write_text("inner one\n\n{a}`b`\n")
+    tmp_path.joinpath("bad_outer.md").write_text(
+        "outer line\n\n```{include} bad_inner.md\n```\n"
+    )
 
     report_stream = StringIO()
     publish_doctree(