diff --git a/src/insets/InsetIndex.cpp b/src/insets/InsetIndex.cpp
index 02a3706961..573ad66ce5 100644
--- a/src/insets/InsetIndex.cpp
+++ b/src/insets/InsetIndex.cpp
@@ -662,9 +662,12 @@ struct IndexEntry
 
 bool operator<(IndexEntry const & lhs, IndexEntry const & rhs)
 {
-	return lhs.main < rhs.main
-			|| (lhs.main == rhs.main && lhs.sub < rhs.sub)
-			|| (lhs.main == rhs.main && lhs.sub == rhs.sub && lhs.subsub < rhs.subsub);
+	int comp = compare_no_case(lhs.main, rhs.main);
+	if (comp == 0)
+		comp = compare_no_case(lhs.sub, rhs.sub);
+	if (comp == 0)
+		comp = compare_no_case(lhs.subsub, rhs.subsub);
+	return (comp < 0);
 }
 
 } // anon namespace