-(defvar tar-regexp "\\.\\(tar\\|tgz\\|tar\\.gz\\)\\'"
- "The regular expression used to identify tar file names.")
+(defvar tar-regexp "\\.tar$"
+ "The regular expression used to identify tar file names.
+Note that this regular expression must not match compressed tar file
+names; if it does, tar-mode will attempt to parse the compressed tar
+file as an uncompressed tar file, which will generate an error. This
+is not a problem, as other modules that handle compression will
+uncompress the buffer and call `tar-mode' appropriately.")