diff --git a/dumux/discretization/projection/projector.hh b/dumux/discretization/projection/projector.hh
index a4a3824d97dcebcfac072fbe81530c8cd2be5c5a..147bcdeca7e800711b4c1aacac6cf59aec6f217a 100644
--- a/dumux/discretization/projection/projector.hh
+++ b/dumux/discretization/projection/projector.hh
@@ -245,7 +245,8 @@ makeProjectorPair(const FEBasisDomain& feBasisDomain,
                 {
                     const auto dofIdxDomain = domainLocalView.index(i);
                     const auto domainShapeVal = domainShapeVals[i];
-                    backwardM[dofIdxDomain][dofIdxDomain] += ie*weight*domainShapeVal;
+                    if (doBidirectional)
+                        backwardM[dofIdxDomain][dofIdxDomain] += ie*weight*domainShapeVal;
 
                     for (unsigned int j = 0; j < targetLocalBasis.size(); ++j)
                     {