diff --git a/weasyprint/css/validation.py b/weasyprint/css/validation.py
index 2912e77e..08f96f9d 100644
--- a/weasyprint/css/validation.py
+++ b/weasyprint/css/validation.py
@@ -1585,8 +1585,7 @@ def validate_content_list_token(token):
         elif prototype in (('content', ()), ('content', ('ident',))):
             if not args:
                 return (name, 'text')
-            elif args[0] in ('text', 'after', 'before'):
-                # TODO: first-letter should be allowed here too
+            elif args[0] in ('text', 'after', 'before', 'first-letter'):
                 return (name, args[0])
         elif prototype in (('counter', ('ident',)),
                            ('counters', ('ident', 'string'))):
diff --git a/weasyprint/formatting_structure/build.py b/weasyprint/formatting_structure/build.py
index 38c304cc..dbe5ae45 100644
--- a/weasyprint/formatting_structure/build.py
+++ b/weasyprint/formatting_structure/build.py
@@ -1159,6 +1159,11 @@ def box_text(box):
         return ''
 
 
+def box_text_first_letter(box):
+    text = box_text(box)
+    return text[0] if text else ''
+
+
 def box_text_before(box):
     if isinstance(box, boxes.ParentBox):
         return ''.join(
@@ -1182,4 +1187,5 @@ def box_text_after(box):
 TEXT_CONTENT_EXTRACTORS = {
     'text': box_text,
     'before': box_text_before,
-    'after': box_text_after}
+    'after': box_text_after,
+    'first-letter': box_text_first_letter}