diff --git a/README.md b/README.md
index d5f5dc9..844a149 100644
--- a/README.md
+++ b/README.md
@@ -7,3 +7,4 @@
 # Features
 - Fixes subtitle numbering
 - Removes lines which have words listed in `~/.config/fsubrc`
+- Backs up the file to a .bak (removed when no error happens)
diff --git a/fsub b/fsub
index 6cc963d..4a56445 100755
--- a/fsub
+++ b/fsub
@@ -14,6 +14,7 @@ usage() {
 [ -z $2 ] || usage
 [ -f $FSUBRC ] || touch $FSUBRC
 
+cp $1 $1.bak
 awk '
 BEGIN {
 	n = 1
@@ -45,3 +46,4 @@ BEGIN {
 		print lines[j]
 }' $1 | sed 's/\r//' > /tmp/fsub
 mv /tmp/fsub $1
+rm $1.bak