diff --git a/Notebooks/Chap15/15_2_Wasserstein_Distance.ipynb b/Notebooks/Chap15/15_2_Wasserstein_Distance.ipynb
index b0561b6..ff7724f 100644
--- a/Notebooks/Chap15/15_2_Wasserstein_Distance.ipynb
+++ b/Notebooks/Chap15/15_2_Wasserstein_Distance.ipynb
@@ -128,7 +128,7 @@
     {
       "cell_type": "code",
       "source": [
-        "draw_2D_heatmap(dist_mat,'Distance $|i-j|$', my_colormap)"
+        "draw_2D_heatmap(dist_mat,r'Distance $|i-j|$', my_colormap)"
       ],
       "metadata": {
         "id": "G0HFPBXyHT6V"
@@ -197,7 +197,7 @@
       "cell_type": "code",
       "source": [
         "TP = np.array(opt.x).reshape(10,10)\n",
-        "draw_2D_heatmap(TP,'Transport plan $\\mathbf{P}$', my_colormap)"
+        "draw_2D_heatmap(TP,r'Transport plan $\\mathbf{P}$', my_colormap)"
       ],
       "metadata": {
         "id": "nZGfkrbRV_D0"