diff --git a/alib2data_experimental/src/indexes/stringology/CompactSuffixAutomatonTerminatingSymbol.h b/alib2data_experimental/src/indexes/stringology/CompactSuffixAutomatonTerminatingSymbol.h
index 7286bab82e5facac4b2a5b0fe13ab719b8379f03..139ed20f56df7c152d04dda2075503925c3a78bc 100644
--- a/alib2data_experimental/src/indexes/stringology/CompactSuffixAutomatonTerminatingSymbol.h
+++ b/alib2data_experimental/src/indexes/stringology/CompactSuffixAutomatonTerminatingSymbol.h
@@ -47,7 +47,8 @@ public:
 
 	void insertVertex(unsigned vertexNumber, const ext::map<ext::pair< int,int>,int> & edges) {
 		for(const auto & edge : edges ) {
-			m_delta[vertexNumber].insert({{edge.first.first - 1, edge.first.second - 1}, edge.second}); // to match indexing the string from 0
+			// FIXME the construction algo works on integers but the datastructure is defined with unsigneds
+			m_delta[vertexNumber].insert({{edge.first.first - 1, edge.first.second - 1}, static_cast < unsigned > ( edge.second ) }); // to match indexing the string from 0
 		}
 	}