diff --git a/prepare-iso.sh b/prepare-iso.sh
index f84bdb8..077fd91 100755
--- a/prepare-iso.sh
+++ b/prepare-iso.sh
@@ -7,6 +7,7 @@
 #   - Sierra (10.12)
 #   - High Sierra (10.13)
 #   - Mojave (10.14)
+#   - Catalina (10.15)
 
 set -e
 
@@ -51,8 +52,11 @@ function createISO()
     echo
     echo Create ${isoName} blank ISO image with a Single Partition - Apple Partition Map
     echo --------------------------------------------------------------------------
-    echo $ hdiutil create -o /tmp/${isoName} -size 8g -layout SPUD -fs HFS+J -type SPARSE
-    hdiutil create -o /tmp/${isoName} -size 8g -layout SPUD -fs HFS+J -type SPARSE
+    # Just in case - delete any previous sparseimage
+    [ -e /tmp/${isoName}.sparseimage ] && rm -f /tmp/${isoName}.sparseimage
+    # increased size to 16G - 8G is too small for Catalina
+    echo $ hdiutil create -o /tmp/${isoName} -size 16g -layout SPUD -fs HFS+J -type SPARSE
+    hdiutil create -o /tmp/${isoName} -size 16g -layout SPUD -fs HFS+J -type SPARSE
 
     echo
     echo Mount the sparse bundle for package addition
@@ -63,9 +67,15 @@ function createISO()
     echo
     echo Restore the Base System into the ${isoName} ISO image
     echo --------------------------------------------------------------------------
-    if [ "${isoName}" == "HighSierra" ] || [ "${isoName}" == "Mojave" ] ; then
+    if [ "${isoName}" == "HighSierra" ] || [ "${isoName}" == "Mojave" ] || [ "${isoName}" == "Catalina" ] ; then
       echo $ asr restore -source "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
-      asr restore -source "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
+      #following asr command returns an error and prints:
+      #"Personalization succeeded
+      #"asr: Couldn't personalize volume /Volumes/macOS Base System - Operation not permitted
+      #I disabled SIP and the error still occurs.
+      #This was reported in Issue #73 for Mojave
+      #I added ||true for now to prevent the script from exiting as the steps that follow still seem to work fine for Catalina
+      asr restore -source "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase  ||true
     else
       echo $ asr restore -source /Volumes/install_app/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
       asr restore -source /Volumes/install_app/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
@@ -74,7 +84,10 @@ function createISO()
     echo
     echo Remove Package link and replace with actual files
     echo --------------------------------------------------------------------------
-    if [ "${isoName}" == "HighSierra" ] || [ "${isoName}" == "Mojave" ] ; then
+    if [ "${isoName}" == "Mojave" ] || [ "${isoName}" == "Catalina" ] ; then
+      echo $ ditto -V /Volumes/install_app/Packages /Volumes/macOS\ Base\ System/System/Installation/
+      ditto -V /Volumes/install_app/Packages /Volumes/macOS\ Base\ System/System/Installation/
+    elif [ "${isoName}" == "HighSierra" ] ; then
       echo $ ditto -V /Volumes/install_app/Packages /Volumes/OS\ X\ Base\ System/System/Installation/
       ditto -V /Volumes/install_app/Packages /Volumes/OS\ X\ Base\ System/System/Installation/
     else
@@ -87,7 +100,12 @@ function createISO()
     echo
     echo Copy macOS ${isoName} installer dependencies
     echo --------------------------------------------------------------------------
-    if [ "${isoName}" == "HighSierra" ] || [ "${isoName}" == "Mojave" ] ; then
+    if [ "${isoName}" == "Mojave" ] || [ "${isoName}" == "Catalina" ] ; then
+      echo $ ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.chunklist /Volumes/macOS\ Base\ System/BaseSystem.chunklist
+      ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.chunklist /Volumes/macOS\ Base\ System/BaseSystem.chunklist
+      echo $ ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg /Volumes/macOS\ Base\ System/BaseSystem.dmg
+      ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg /Volumes/macOS\ Base\ System/BaseSystem.dmg
+    elif [ "${isoName}" == "HighSierra" ] ; then
       echo $ ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
       ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
       echo $ ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg
@@ -108,9 +126,13 @@ function createISO()
     echo
     echo Unmount the sparse bundle
     echo --------------------------------------------------------------------------
-    echo $ hdiutil detach /Volumes/OS\ X\ Base\ System/
-    hdiutil detach /Volumes/OS\ X\ Base\ System/
-
+    if [ "${isoName}" == "Mojave" ] || [ "${isoName}" == "Catalina" ] ; then
+      echo $ hdiutil detach /Volumes/macOS\ Base\ System/
+      hdiutil detach /Volumes/macOS\ Base\ System/
+    else
+      echo $ hdiutil detach /Volumes/OS\ X\ Base\ System/
+      hdiutil detach /Volumes/OS\ X\ Base\ System/
+    fi
     echo
     echo Resize the partition in the sparse bundle to remove any free space
     echo --------------------------------------------------------------------------
@@ -158,29 +180,34 @@ function installerExists()
 # Main script code
 #
 # Eject installer disk in case it was opened after download from App Store
-for disk in $(hdiutil info | grep /dev/disk | grep partition | cut -f 1); do
+# grep "partition_scheme" because "partition" finds too many lines
+for disk in $(hdiutil info | grep /dev/disk | grep partition_scheme | cut -f 1); do
   hdiutil detach -force ${disk}
 done
 
 # See if we can find an eligible installer.
 # If successful, then create the iso file from the installer.
 
-if installerExists "Install macOS Mojave.app" ; then
-  createISO "Install macOS Mojave.app" "Mojave"
+if installerExists "Install macOS Catalina.app" ; then
+  createISO "Install macOS Catalina.app" "Catalina"
 else
-  if installerExists "Install macOS High Sierra.app" ; then
-    createISO "Install macOS High Sierra.app" "HighSierra"
+  if installerExists "Install macOS Mojave.app" ; then
+    createISO "Install macOS Mojave.app" "Mojave"
   else
-    if installerExists "Install macOS Sierra.app" ; then
-      createISO "Install macOS Sierra.app" "Sierra"
+    if installerExists "Install macOS High Sierra.app" ; then
+      createISO "Install macOS High Sierra.app" "HighSierra"
     else
-      if installerExists "Install OS X El Capitan.app" ; then
-        createISO "Install OS X El Capitan.app" "ElCapitan"
+      if installerExists "Install macOS Sierra.app" ; then
+        createISO "Install macOS Sierra.app" "Sierra"
       else
-        if installerExists "Install OS X Yosemite.app" ; then
-          createISO "Install OS X Yosemite.app" "Yosemite"
+        if installerExists "Install OS X El Capitan.app" ; then
+          createISO "Install OS X El Capitan.app" "ElCapitan"
         else
-          echo "Could not find installer for Yosemite (10.10), El Capitan (10.11), Sierra (10.12), High Sierra (10.13) or Mojave (10.14)."
+          if installerExists "Install OS X Yosemite.app" ; then
+            createISO "Install OS X Yosemite.app" "Yosemite"
+          else
+            echo "Could not find installer for Yosemite (10.10), El Capitan (10.11), Sierra (10.12), High Sierra (10.13), Mojave (10.14) or Catalina (10.15)."
+          fi
         fi
       fi
     fi