diff --git a/notebooks/STIS/contrast_sensitivity/STIS_Coronagraphic_Observation_Feasibility.ipynb b/notebooks/STIS/contrast_sensitivity/STIS_Coronagraphic_Observation_Feasibility.ipynb
index e2eb0e092..1c306d725 100644
--- a/notebooks/STIS/contrast_sensitivity/STIS_Coronagraphic_Observation_Feasibility.ipynb
+++ b/notebooks/STIS/contrast_sensitivity/STIS_Coronagraphic_Observation_Feasibility.ipynb
@@ -243,7 +243,7 @@
     "        None        \n",
     "          \n",
     "    if feature == 'companion':\n",
-    "        if 'comp_sep' == None or 'comp_contrast' == None:\n",
+    "        if comp_sep is None or comp_contrast is None:\n",
     "            raise NameError(\"Companion separation ('comp_sep') or companion contrast ('comp_contrast') or  not specified.\")     \n",
     "        comp_separation = comp_sep\n",
     "        comp_contrast = comp_contrast\n",
@@ -257,13 +257,13 @@
     "        diskprofile = disk_profile\n",
     "        \n",
     "        if diskprofile == 'flat':\n",
-    "            if 'disk_contrast' == None:\n",
+    "            if disk_contrast is None:\n",
     "                raise NameError(\"Disk contrast not specified.\")\n",
     "            diskcontrast = disk_contrast\n",
     "            plt.axhline(diskcontrast, ls='--', linewidth=4, color='orange', label=target_name)\n",
     "            \n",
     "        elif diskprofile == 'sb_profile':\n",
-    "            if 'disk_filename' == None:\n",
+    "            if disk_filename is None:\n",
     "                raise NameError(\"Surface brightness profile file name is not specified.\")\n",
     "        \n",
     "            diskfilename = disk_filename\n",
@@ -272,13 +272,13 @@
     "            disk_cont = disk_sb_profile[:, 1]\n",
     "            plt.plot(disk_r, disk_cont, ls='--', linewidth=4, color='orange', label=target_name)\n",
     "            \n",
-    "        elif diskprofile == None:\n",
+    "        elif diskprofile is None:\n",
     "            None\n",
     "            \n",
     "        else:\n",
     "            raise NameError(\"Disk profile not specified. Must be either 'flat' or 'sb_profile'.\")\n",
     "           \n",
-    "    elif feature == None:\n",
+    "    elif feature is None:\n",
     "        None\n",
     "        \n",
     "    plt.legend(fontsize=18, loc='best', markerscale=0.5)\n",