diff --git a/ontologies/small_math.thy b/ontologies/small_math.thy
index c9b6705..6a1bb70 100644
--- a/ontologies/small_math.thy
+++ b/ontologies/small_math.thy
@@ -10,7 +10,7 @@ doc_class title =
 doc_class author =
    email       :: "string" <= "''''"
 
-datatype classification = algebra | geometry | graph_theory
+datatype classification = algebra | geometry | topology
 
 doc_class abstract =
     keyword_list :: "classification list"   <= "[]"