diff --git a/CHANGES b/CHANGES
index 42377f34c1e..9d2890b8e93 100644
--- a/CHANGES
+++ b/CHANGES
@@ -18,6 +18,8 @@ Features added
 
 * #10366: std domain: Add support for emphasising placeholders in :rst:dir`option`
   directives through a new ``option_emphasise_placeholders`` configuration option.
+* #10439: std domain: Use the repr of some variables when displaying warnings,
+  making whitespace issues easier to identify.
 
 Bugs fixed
 ----------
diff --git a/sphinx/domains/std.py b/sphinx/domains/std.py
index 8ff199ade50..88a4d28cb8a 100644
--- a/sphinx/domains/std.py
+++ b/sphinx/domains/std.py
@@ -601,11 +601,11 @@ class StandardDomain(Domain):
     }
 
     dangling_warnings = {
-        'term': 'term not in glossary: %(target)s',
-        'numref':  'undefined label: %(target)s',
-        'keyword': 'unknown keyword: %(target)s',
-        'doc': 'unknown document: %(target)s',
-        'option': 'unknown option: %(target)s',
+        'term': 'term not in glossary: %(target)r',
+        'numref':  'undefined label: %(target)r',
+        'keyword': 'unknown keyword: %(target)r',
+        'doc': 'unknown document: %(target)r',
+        'option': 'unknown option: %(target)r',
     }
 
     # node_class -> (figtype, title_getter)
@@ -1100,9 +1100,9 @@ def warn_missing_reference(app: "Sphinx", domain: Domain, node: pending_xref
     else:
         target = node['reftarget']
         if target not in domain.anonlabels:  # type: ignore
-            msg = __('undefined label: %s')
+            msg = __('undefined label: %r')
         else:
-            msg = __('Failed to create a cross reference. A title or caption not found: %s')
+            msg = __('Failed to create a cross reference. A title or caption not found: %r')
 
         logger.warning(msg % target, location=node, type='ref', subtype=node['reftype'])
         return True
diff --git a/tests/test_build_html.py b/tests/test_build_html.py
index 3ef0e36550d..bae871db1f7 100644
--- a/tests/test_build_html.py
+++ b/tests/test_build_html.py
@@ -39,7 +39,7 @@
 """
 
 HTML_WARNINGS = ENV_WARNINGS + """\
-%(root)s/index.rst:\\d+: WARNING: unknown option: &option
+%(root)s/index.rst:\\d+: WARNING: unknown option: '&option'
 %(root)s/index.rst:\\d+: WARNING: citation not found: missing
 %(root)s/index.rst:\\d+: WARNING: a suitable image for html builder not found: foo.\\*
 %(root)s/index.rst:\\d+: WARNING: Could not lex literal_block as "c". Highlighting skipped.
diff --git a/tests/test_build_latex.py b/tests/test_build_latex.py
index 709dce05db4..9a325a8d469 100644
--- a/tests/test_build_latex.py
+++ b/tests/test_build_latex.py
@@ -25,7 +25,7 @@
               'fncychap.sty', 'geometry.sty', 'kvoptions.sty', 'hyperref.sty']
 
 LATEX_WARNINGS = ENV_WARNINGS + """\
-%(root)s/index.rst:\\d+: WARNING: unknown option: &option
+%(root)s/index.rst:\\d+: WARNING: unknown option: '&option'
 %(root)s/index.rst:\\d+: WARNING: citation not found: missing
 %(root)s/index.rst:\\d+: WARNING: a suitable image for latex builder not found: foo.\\*
 %(root)s/index.rst:\\d+: WARNING: Could not lex literal_block as "c". Highlighting skipped.
diff --git a/tests/test_build_texinfo.py b/tests/test_build_texinfo.py
index 772644abea0..5c72a34490b 100644
--- a/tests/test_build_texinfo.py
+++ b/tests/test_build_texinfo.py
@@ -17,7 +17,7 @@
 from .test_build_html import ENV_WARNINGS
 
 TEXINFO_WARNINGS = ENV_WARNINGS + """\
-%(root)s/index.rst:\\d+: WARNING: unknown option: &option
+%(root)s/index.rst:\\d+: WARNING: unknown option: '&option'
 %(root)s/index.rst:\\d+: WARNING: citation not found: missing
 %(root)s/index.rst:\\d+: WARNING: a suitable image for texinfo builder not found: foo.\\*
 %(root)s/index.rst:\\d+: WARNING: a suitable image for texinfo builder not found: \
diff --git a/tests/test_domain_py.py b/tests/test_domain_py.py
index baad0c2daa2..ce1636eb28e 100644
--- a/tests/test_domain_py.py
+++ b/tests/test_domain_py.py
@@ -1369,6 +1369,6 @@ def test_python_python_use_unqualified_type_names_disabled(app, status, warning)
 @pytest.mark.sphinx('dummy', testroot='domain-py-xref-warning')
 def test_warn_missing_reference(app, status, warning):
     app.build()
-    assert 'index.rst:6: WARNING: undefined label: no-label' in warning.getvalue()
-    assert ('index.rst:6: WARNING: Failed to create a cross reference. A title or caption not found: existing-label'
-            in warning.getvalue())
+    assert "index.rst:6: WARNING: undefined label: 'no-label'" in warning.getvalue()
+    assert ("index.rst:6: WARNING: Failed to create a cross reference. "
+            "A title or caption not found: 'existing-label'") in warning.getvalue()
diff --git a/tests/test_ext_autosectionlabel.py b/tests/test_ext_autosectionlabel.py
index f950b8f1d9b..f99a6d3f60a 100644
--- a/tests/test_ext_autosectionlabel.py
+++ b/tests/test_ext_autosectionlabel.py
@@ -74,4 +74,4 @@ def test_autosectionlabel_maxdepth(app, status, warning):
     html = '<li><p><span class="xref std std-ref">Linux</span></p></li>'
     assert re.search(html, content, re.S)
 
-    assert 'WARNING: undefined label: linux' in warning.getvalue()
+    assert "WARNING: undefined label: 'linux'" in warning.getvalue()