diff --git a/to_png.py b/to_png.py
index 83f15ea..667ad5e 100644
--- a/to_png.py
+++ b/to_png.py
@@ -10,7 +10,7 @@ pixel to fully transparent, and writes a PNG.
 Usage:
     python3 to_png.py [dir ...]          # default: all gfx*_extracted dirs
     python3 to_png.py --key RRGGBB ...   # custom colorkey (hex), default 000000
-    python3 to_png.py --keep             # keep .bmp files (default keeps them)
+    python3 to_png.py --keep             # keep .bmp files (default deletes them)
 """
 import sys, os, glob
 from PIL import Image
@@ -30,6 +30,7 @@ def convert(path, key):
 def main():
     args = sys.argv[1:]
     key = (0, 0, 0)
+    keep = False
     dirs = []
     i = 0
     while i < len(args):
@@ -37,6 +38,8 @@ def main():
             h = args[i+1].lstrip('#')
             key = (int(h[0:2], 16), int(h[2:4], 16), int(h[4:6], 16))
             i += 2
+        elif args[i] == '--keep':
+            keep = True; i += 1
         else:
             dirs.append(args[i]); i += 1
     if not dirs:
@@ -47,6 +50,8 @@ def main():
         for b in bmps:
             try:
                 convert(b, key)
+                if not keep:
+                    os.remove(b)
                 total += 1
             except Exception as ex:
                 print('  ERROR %s: %s' % (b, ex))
@@ -54,4 +59,4 @@ def main():
     print('TOTAL %d png (colorkey %02x%02x%02x)' % (total, *key))
 
 if __name__ == '__main__':
-    main()
+    main()
\ No newline at end of file