diff --git a/lecture_014/A_Practitioners_Guide_to_Triton.ipynb b/lecture_014/A_Practitioners_Guide_to_Triton.ipynb
index af4503e..ff20146 100644
--- a/lecture_014/A_Practitioners_Guide_to_Triton.ipynb
+++ b/lecture_014/A_Practitioners_Guide_to_Triton.ipynb
@@ -423,14 +423,14 @@
     "    mask = offs < n # <- this is a vector of bools!\n",
     "    \n",
     "    # read data\n",
-    "    x_values = x[offs] # <- a vector is read!\n",
-    "    y_values = y[offs] # <- a vector is read!\n",
+    "    x_values = x[offs[mask]] # <- a vector is read!\n",
+    "    y_values = y[offs[mask]] # <- a vector is read!\n",
     "    \n",
     "    # do operation\n",
     "    z_value = x_value + y_value  # <- vectors are added!\n",
     "    \n",
     "    # write data\n",
-    "    z[offs] = z_value  # <- a vector is written!"
+    "    z[offs[mask]] = z_value  # <- a vector is written!"
    ]
   },
   {