diff --git a/dune/gdt/assembler/system.hh b/dune/gdt/assembler/system.hh
index daed1b6a6ec6b0799824bcd458c38f907ddd07ff..f61c7d770c7ef4db73ee73a30f18773d5f712d3a 100644
--- a/dune/gdt/assembler/system.hh
+++ b/dune/gdt/assembler/system.hh
@@ -201,8 +201,7 @@ public:
     this->walk(partitioning);
   }
 
-
-private:
+protected:
   const DS::PerThreadValue<const TestSpaceType> test_space_;
   const DS::PerThreadValue<const AnsatzSpaceType> ansatz_space_;
 }; // class SystemAssembler