diff --git a/opm/core/transport/reorder/tarjan.c b/opm/core/transport/reorder/tarjan.c
index 320244533..d3245610b 100644
--- a/opm/core/transport/reorder/tarjan.c
+++ b/opm/core/transport/reorder/tarjan.c
@@ -196,7 +196,7 @@ tarjan (int nv, const int *ia, const int *ja, int *vert, int *comp,
                 }
                 else
                 {
-                    assert(status[child] = DONE);
+                    assert(status[child] == DONE);
                 }
             }
         }