diff --git a/dune/istl/colcompmatrix.hh b/dune/istl/colcompmatrix.hh
index 7988eb84ca1122a05154d6cb7e4689ff80526919..becf80a264e64e5e65e9438fad2b90ca89101831 100644
--- a/dune/istl/colcompmatrix.hh
+++ b/dune/istl/colcompmatrix.hh
@@ -157,7 +157,7 @@ namespace Dune
   template<class Mat>
   class ColCompMatrix
   {
-    friend struct ColCompMatrixInitializer<Mat>;
+    friend class ColCompMatrixInitializer<Mat>;
 
     using B = typename Mat::field_type;