diff --git a/mkmp4.sh b/mkmp4.bash
similarity index 79%
rename from mkmp4.sh
rename to mkmp4.bash
index 40230df..0f89e39 100755
--- a/mkmp4.sh
+++ b/mkmp4.bash
@@ -1,4 +1,4 @@
-#!/usr/bin/env sh
+#!/usr/bin/env bash
 
 # Daniel Bowling <swaggboi@slackware.uk>
 # Dec 2020
@@ -31,21 +31,21 @@ conv_vid() {
     for file in "$PWD"/*; do
         if [ -f "$file" ]; then
             case "$file" in
-                *".M4V"|*".m4v")
+                *".m4v")
                     oldfile=$file
-                    newfile=${oldfile/+(.M4V|.m4v)/.mp4}
+                    newfile=${oldfile/%.m4v/.mp4}
                     ;;
-                *".AVI"|*".avi")
+                *".avi")
                     oldfile=$file
-                    newfile=${oldfile/+(.AVI|.avi)/.mp4}
+                    newfile=${oldfile/%.avi/.mp4}
                     ;;
-                *".MKV"|*".mkv")
+                *".mkv")
                     oldfile=$file
-                    newfile=${oldfile/+(.MKV|.mkv)/.mp4}
+                    newfile=${oldfile/%.mkv/.mp4}
                     ;;
-                *".MP4"|*".mp4")
+                *".mp4")
                     oldfile=$file
-                    newfile=${oldfile/+(.MP4|.mp4)/.NEW.mp4}
+                    newfile=${oldfile/%.mp4/.NEW.mp4}
                     ;;
                 *)
                     # Next iteration of big ol loop