diff --git a/dumux/implicit/box/boxfvelementgeometry.hh b/dumux/implicit/box/boxfvelementgeometry.hh
index 768c4c18269fddde83147ab7ac0ac49b325381f8..c04cbe78d99200a9a434e53eebdcbbad535ece82 100644
--- a/dumux/implicit/box/boxfvelementgeometry.hh
+++ b/dumux/implicit/box/boxfvelementgeometry.hh
@@ -674,7 +674,7 @@ public:
                     diffVec[m] -= subContVol[i].global[m];
                 // make sure the normal points to the right direction
                 if (subContVolFace[k].normal * diffVec < 0)
-                    subContVolFace[k].normal *= -1;
+                    subContVolFace[k].normal *= -1.0;
             }
             else if (dim==3) {
                 int leftFace;