diff --git a/CHANGES b/CHANGES
index 28e89863f..b61fdd58b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -16,6 +16,7 @@ Deprecated
 Features added
 --------------
 
+* #9103: LaTeX: imgconverter: conversion runs even if not needed
 * #9023: More CSS classes on domain descriptions, see :ref:`nodes` for details.
 
 Bugs fixed
diff --git a/sphinx/transforms/post_transforms/images.py b/sphinx/transforms/post_transforms/images.py
index f9b78837f..c9ed572b8 100644
--- a/sphinx/transforms/post_transforms/images.py
+++ b/sphinx/transforms/post_transforms/images.py
@@ -197,7 +197,7 @@ class ImageConverter(BaseImageConverter):
     def match(self, node: nodes.image) -> bool:
         if not self.app.builder.supported_image_types:
             return False
-        elif set(node['candidates']) & set(self.app.builder.supported_image_types):
+        elif set(self.guess_mimetypes(node)) & set(self.app.builder.supported_image_types):
             # builder supports the image; no need to convert
             return False
         elif self.available is None:
diff --git a/tests/roots/test-ext-imgconverter/img.pdf b/tests/roots/test-ext-imgconverter/img.pdf
new file mode 100644
index 000000000..cacbd855d
Binary files /dev/null and b/tests/roots/test-ext-imgconverter/img.pdf differ
diff --git a/tests/roots/test-ext-imgconverter/index.rst b/tests/roots/test-ext-imgconverter/index.rst
index 786c92e8d..f8ef1d6e2 100644
--- a/tests/roots/test-ext-imgconverter/index.rst
+++ b/tests/roots/test-ext-imgconverter/index.rst
@@ -2,3 +2,4 @@ test-ext-imgconverter
 =====================
 
 .. image:: svgimg.svg
+.. image:: img.pdf
diff --git a/tests/test_ext_imgconverter.py b/tests/test_ext_imgconverter.py
index 5f6f236cf..b4fd46d25 100644
--- a/tests/test_ext_imgconverter.py
+++ b/tests/test_ext_imgconverter.py
@@ -19,6 +19,11 @@ def test_ext_imgconverter(app, status, warning):
     app.builder.build_all()
 
     content = (app.outdir / 'python.tex').read_text()
+
+    # supported image (not converted)
+    assert '\\sphinxincludegraphics{{img}.pdf}' in content
+
+    # non supported image (converted)
     assert '\\sphinxincludegraphics{{svgimg}.png}' in content
     assert not (app.outdir / 'svgimg.svg').exists()
     assert (app.outdir / 'svgimg.png').exists()