diff --git a/pungi/wrappers/variants.py b/pungi/wrappers/variants.py
index 1c3949d3..47822014 100755
--- a/pungi/wrappers/variants.py
+++ b/pungi/wrappers/variants.py
@@ -150,7 +150,11 @@ class VariantsXmlParser(object):
             self.add_child(optional, variant)
 
         for ref in variant_node.xpath("variants/ref/@id"):
-            child_variant = self.parse_variant_node(self.addons[ref], variant)
+            try:
+                child_variant = self.parse_variant_node(self.addons[ref], variant)
+            except KeyError:
+                raise RuntimeError("Variant %s references non-existing variant %s"
+                                   % (variant.uid, ref))
             self.add_child(child_variant, variant)
 
 # XXX: top-level optional
diff --git a/share/variants.dtd b/share/variants.dtd
index 49d48813..19ef3430 100644
--- a/share/variants.dtd
+++ b/share/variants.dtd
@@ -2,7 +2,7 @@
 
 <!ELEMENT variant (release?,arches,groups?,environments*,variants*,buildinstallpackages?)?>
 <!ATTLIST variant
-    id ID #REQUIRED
+    id CDATA #REQUIRED
     name CDATA #REQUIRED
     type (variant|addon|optional|layered-product) #REQUIRED
     has_optional (true|false) #IMPLIED
@@ -39,7 +39,7 @@
 
 <!ELEMENT ref EMPTY>
 <!ATTLIST ref
-    id IDREF #REQUIRED
+    id CDATA #REQUIRED
 >
 
 <!ELEMENT buildinstallpackages (package)+>