diff --git a/masking_and_moments/masking_and_moments_guide.ipynb b/masking_and_moments/masking_and_moments_guide.ipynb
index 226bdc4..f57d78c 100644
--- a/masking_and_moments/masking_and_moments_guide.ipynb
+++ b/masking_and_moments/masking_and_moments_guide.ipynb
@@ -85,7 +85,7 @@
     "    cache=True, show_progress=True)\n",
     "\n",
     "# Note that the datafile will not end in \".fits\". Because of that, we need to specify the format\n",
-    "# When the file name end in \"fits\", `format` will not need to be specified \n",
+    "# When the file name end in \"fits\", `format` will not need to be specified\n",
     "cube = SpectralCube.read(filename, format='fits', use_dask=False)\n",
     "\n",
     "# Convert to km/s for the spectral unit\n",
@@ -460,7 +460,7 @@
     "\n",
     "# Add 1 spectral element on each side of the spatial structure.\n",
     "# np.dstack stacks the arrays along a new 3rd dimension:\n",
-    "structure = np.dstack([structure_spec, structure, structure_spec])\n",
+    "structure = np.swapaxes(np.dstack([structure_spec, structure, structure_spec]), 0, 2)\n",
     "\n",
     "signal_mask = nd.binary_dilation(signal_mask, structure=structure, iterations=1)\n"
    ]
@@ -956,7 +956,7 @@
    "source": [
     "with warnings.catch_warnings():\n",
     "    warnings.simplefilter('ignore')\n",
-    "    \n",
+    "\n",
     "    # Load cube\n",
     "    cube = SpectralCube.read(filename, format='fits', use_dask=True)\n",
     "    # Convert to km/s for the spectral unit\n",
@@ -996,10 +996,10 @@
     "                                                      label_image=low_snr_mask_labels,\n",
     "                                                      index=range(1, num_labels + 1)) # +1 offset for mask labels\n",
     "\n",
-    "    # To preserve the low_snr_mask, we will create a new signal mask where we will remove \n",
+    "    # To preserve the low_snr_mask, we will create a new signal mask where we will remove\n",
     "    # regions that do not pass the criteria.\n",
     "    signal_mask = low_snr_mask\n",
-    "    # NOTE: this is memory efficient but may be slower than defining a new empty array and adding the \n",
+    "    # NOTE: this is memory efficient but may be slower than defining a new empty array and adding the\n",
     "    #       (often fewer) number of regions that pass the minimum pixel criteria. See the scipy example\n",
     "    #       above on using this alternative approach.\n",
     "\n",