diff --git a/examples/testInterface.ipynb b/examples/testInterface.ipynb
index 78ca302c40df57c568665d2d4a80b6ccebd106f9..54a153d0238e2615ce9842608479646663d8c560 100644
--- a/examples/testInterface.ipynb
+++ b/examples/testInterface.ipynb
@@ -171,7 +171,7 @@
     "    dict\n",
     "        Mean-field tb model.\n",
     "    \"\"\"\n",
-    "    exchange = {vec: -1*(int_model.get(vec, 0) + rhoTbfunc(vec)) for vec in frozenset(int_model)}\n",
+    "    exchange = {vec: -1*(int_model.get(vec, 0)*rhoTbfunc(vec)) for vec in frozenset(int_model)}\n",
     "    # direct interaction is missing\n",
     "    return exchange"
    ]