diff --git a/boards/forms.py b/boards/forms.py
--- a/boards/forms.py
+++ b/boards/forms.py
@@ -214,15 +214,14 @@ class ThreadForm(PostForm):
 
     tags = forms.CharField(
         widget=forms.TextInput(attrs={ATTRIBUTE_PLACEHOLDER: TAGS_PLACEHOLDER}),
-        max_length=100, label=_('Tags'))
+        max_length=100, label=_('Tags'), required=True)
 
     def clean_tags(self):
         tags = self.cleaned_data['tags'].strip()
 
-        if tags:
-            if not self.regex_tags.match(tags):
-                raise forms.ValidationError(
-                    _('Inappropriate characters in tags.'))
+        if not tags or not self.regex_tags.match(tags):
+            raise forms.ValidationError(
+                _('Inappropriate characters in tags.'))
 
         return tags