diff --git a/README.md b/README.md
index 2aa1c93..002f527 100644
--- a/README.md
+++ b/README.md
@@ -194,6 +194,7 @@ The following environment variables are available in Docker.  They will default
 | LRC_FOR_AUDIO_FILES | True | Will generate LRC (instead of SRT) files for filetypes: '.mp3', '.flac', '.wav', '.alac', '.ape', '.ogg', '.wma', '.m4a', '.m4b', '.aac', '.aiff' | 
 | CUSTOM_REGROUP | 'cm_sl=84_sl=42++++++1' | Attempts to regroup some of the segments to make a cleaner looking subtitle.  See https://github.com/McCloudS/subgen/issues/68 for discussion. Set to blank if you want to use Stable-TS default regroups algorithm of `cm_sp=,* /，_sg=.5_mg=.3+3_sp=.* /。/?/？` |
 | DETECT_LANGUAGE_LENGTH | 30 | Detect language on the first x seconds of the audio. |
+| SKIPIFEXTERNALSUB | False | Skip subtitle generation if an external subtitle with the same language code as NAMESUBLANG is present. Used for the case of not regenerating subtitles if I already have `Movie (2002).NAMESUBLANG.srt` from a non-subgen source. |
 
 ### Images:
 `mccloud/subgen:latest` is GPU or CPU <br>