diff --git a/doc/SPEC.md b/doc/SPEC.md
index 696e508..e015e22 100644
--- a/doc/SPEC.md
+++ b/doc/SPEC.md
@@ -41,7 +41,7 @@ A Mews page MUST be a well-formed, valid XHTML-MP 1.2 document that also follows
 
 ### 3.1 Prologue and doctype
 
-A Mews page MUST begin with an XML declaration specifying UTF-8, followed by the XHTML-MP 1.2 doctype:
+A Mews page MUST begin with an XML declaration specifying UTF-8, followed by the XHTML-MP 1.2 doctype. Either quote character may be used in the declaration, as XML allows:
 
 ```xml
 <?xml version="1.0" encoding="UTF-8"?>
diff --git a/mews/lint.py b/mews/lint.py
index da2280f..5ed1b36 100644
--- a/mews/lint.py
+++ b/mews/lint.py
@@ -46,7 +46,12 @@ SIZE_SHOULD = 64 * 1024
 SIZE_TOTAL = 320 * 1024
 IMAGE_SHOULD = 50 * 1024
 
-XML_DECLARATION = re.compile(rb'^<\?xml version="1\.0" encoding="(?i:UTF-8)"\?>')
+# Either quote character, because XML permits both and serialisers differ:
+# lxml writes single quotes. Section 3.1 asks for a declaration naming UTF-8,
+# and its example is one way of writing that rather than the only way.
+XML_DECLARATION = re.compile(
+    rb"^<\?xml\s+version\s*=\s*([\"'])1\.0\1\s+encoding\s*=\s*([\"'])(?i:UTF-8)\2\s*\?>"
+)
 DOCTYPE = re.compile(
     rb'<!DOCTYPE\s+html\s+PUBLIC\s+"-//WAPFORUM//DTD XHTML Mobile 1\.2//EN"\s+'
     rb'"http://www\.openmobilealliance\.org/tech/DTD/xhtml-mobile12\.dtd"\s*>'
diff --git a/tests/test_lint_rules.py b/tests/test_lint_rules.py
index bb9e29f..9b5b1e2 100644
--- a/tests/test_lint_rules.py
+++ b/tests/test_lint_rules.py
@@ -34,6 +34,17 @@ def test_rule_failure_maps_to_its_section(fail_page, name, expected):
     assert (match[0].section, match[0].level) == (section, level)
 
 
+def test_either_quote_character_opens_the_declaration(conforming):
+    """Serialisers differ: lxml writes single quotes, and XML allows them."""
+    page = conforming().replace(
+        b'<?xml version="1.0" encoding="UTF-8"?>',
+        b"<?xml version='1.0' encoding='UTF-8'?>",
+    )
+    report = validate_bytes(page)
+    assert "xml-declaration" not in [f.code for f in report.findings]
+    assert report.conforms
+
+
 def test_entity_declarations_are_refused_before_parsing(fail_page):
     """A page declaring its own entities is rejected without expanding them."""
     report = validate_bytes(fail_page("billion-laughs"))