diff --git a/course_content/iris_course/4.Joining_Cubes_Together.ipynb b/course_content/iris_course/4.Joining_Cubes_Together.ipynb
index 40433d1..08d5eee 100644
--- a/course_content/iris_course/4.Joining_Cubes_Together.ipynb
+++ b/course_content/iris_course/4.Joining_Cubes_Together.ipynb
@@ -294,7 +294,7 @@
    "source": [
     "By inspecting the cubes themselves or using the error message raised when using `merge_cube` we can see that some cubes are missing the `realization` coordinate.\n",
     "\n",
-    "By adding the missing coordinate, we can trigger a merge of the 12 cubes into a single cube, as expected:"
+    "By adding the missing coordinate, we can trigger a merge of the 12 cubes into a single cube, as expected. Make sure both the name and units of the coordinates match the respective coordinate, so that Iris knows they're the same and can be merged together:"
    ]
   },
   {
@@ -306,7 +306,7 @@
     "for cube in cubes:\n",
     "    if not cube.coords('realization'):\n",
     "        cube.add_aux_coord(iris.coords.DimCoord(np.int32(3),\n",
-    "                                                'realization'))\n",
+    "                                                'realization', units ='1'))\n",
     "\n",
     "merged_cube = cubes.merge_cube()\n",
     "print(merged_cube)"
@@ -581,9 +581,9 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "default-current",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
-   "name": "default-current"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
@@ -595,7 +595,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.6.8"
+   "version": "3.9.12"
   }
  },
  "nbformat": 4,
diff --git a/course_content/iris_course/7.Advanced_Concepts.ipynb b/course_content/iris_course/7.Advanced_Concepts.ipynb
index 72dffe2..89f3b69 100644
--- a/course_content/iris_course/7.Advanced_Concepts.ipynb
+++ b/course_content/iris_course/7.Advanced_Concepts.ipynb
@@ -97,7 +97,7 @@
     "    basename = os.path.basename(fname)\n",
     "    if not cube.coords('realization') and basename.startswith('ensemble_'):\n",
     "        cube.add_aux_coord(iris.coords.DimCoord(np.int32(basename[-6:-3]),\n",
-    "                                                'realization'))\n",
+    "                                                'realization', units ='1'))\n",
     "\n",
     "print(iris.load_cube(fname, callback=realization_callback))"
    ]
@@ -534,7 +534,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -548,7 +548,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.6.6"
+   "version": "3.9.12"
   }
  },
  "nbformat": 4,