Index: autotrace-0.31.1/input-bmp.c
===================================================================
--- autotrace-0.31.1.orig/input-bmp.c
+++ autotrace-0.31.1/input-bmp.c
@@ -166,7 +166,8 @@ input_bmp_reader (at_string filename,
                                                         /* 36 */
       Maps = 4;
     }
-  else if (Bitmap_File_Head.biSize <= 64) /* Probably OS/2 2.x */
+  else if (Bitmap_File_Head.biSize >= 56 && Bitmap_File_Head.biSize <= 64)
+    /* enhanced Windows format with bit masks */
     {
       if (!ReadOK (fd, buffer, Bitmap_File_Head.biSize - 4))
 	{