diff --git a/prebuilt/common/bin/backuptool.sh b/prebuilt/common/bin/backuptool.sh
index 9853eed..2f14522 100755
--- a/prebuilt/common/bin/backuptool.sh
+++ b/prebuilt/common/bin/backuptool.sh
@@ -29,12 +29,13 @@
   if [ ! -f /tmp/build.prop ]; then
     # this will block any backups made before 8 cause file was not copied before
     echo "Not restoring files from incompatible version: $V"
-    exit 127
+    return 0
   fi
   if ( ! grep -q "^ro.build.version.release=$V.*" /tmp/build.prop ); then
     echo "Not restoring files from incompatible version: $V"
-    exit 127
+    return 0
   fi
+  return 1
 }
 
 # Execute /system/addon.d/*.sh scripts with $1 parameter
@@ -81,7 +82,10 @@
     cp $S/build.prop /tmp
     mount_system
     mkdir -p $C
-    #check_prereq
+    if ! check_prereq; then
+      unmount_system
+      exit 127
+    end
     preserve_addon_d
     run_stage pre-backup
     run_stage backup
@@ -91,7 +95,10 @@
   restore)
     cp $S/bin/backuptool.functions /tmp
     mount_system
-    check_prereq
+    if ! check_prereq; then
+      unmount_system
+      exit 127
+    end
     run_stage pre-restore
     run_stage restore
     run_stage post-restore
diff --git a/prebuilt/common/bin/backuptool_ab.sh b/prebuilt/common/bin/backuptool_ab.sh
index 2a8c3d9..d542700 100755
--- a/prebuilt/common/bin/backuptool_ab.sh
+++ b/prebuilt/common/bin/backuptool_ab.sh
@@ -50,10 +50,11 @@
     return 0
 fi
 
-grep -q "^ro.omni.version=$V.*" /product/build.prop && return 1
-
-echo "Not backing up files from incompatible version: $V"
-return 0
+if ! grep -q "^ro.omni.version=$V.*" /product/build.prop; then
+    echo "Not backing up files from incompatible version: $V"
+    return 0
+fi
+return 1
 }
 
 # Execute /system/addon.d/*.sh scripts with $1 parameter
@@ -78,10 +79,8 @@
 case "$1" in
   backup)
     mkdir -p $C
-    if check_prereq; then
-        if check_whitelist postinstall/system; then
-            exit 127
-        fi
+    if ! check_prereq; then
+      exit 127
     fi
     log -t "update_engine" "backuptool_ab.sh backup"
 
@@ -91,10 +90,8 @@
     run_stage post-backup
   ;;
   restore)
-    if check_prereq; then
-        if check_whitelist postinstall/tmp; then
-            exit 127
-        fi
+    if ! check_prereq; then
+      exit 127
     fi
     log -t "update_engine" "backuptool_ab.sh restore"