diff --git a/README.md b/README.md
index 7d4a7af..ec456c3 100644
--- a/README.md
+++ b/README.md
@@ -20,8 +20,8 @@ API calls.
Use "-f -" to work on stdout when creating archive or stdin when reading archive
NOTICE: "-f" is not affected by "-C"!
-C
: Change current working directory before archiving/extracting
- --compressor : requires --decompressor
- --decompressor : requires --compressor
+ --compressor : requires --decompressor and cmd must use stdin/stdout
+ --decompressor : requires --compressor and cmd must use stdin/stdout
Specifying "--decompressor" when extracting overrides archive file's stored decompressor cmd
--overwrite-create : allows overwriting an archive file
--overwrite-extract : allows overwriting when extracting
diff --git a/src/parser.c b/src/parser.c
index dd6383a..31a9ea8 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -156,9 +156,11 @@ void simple_archiver_print_usage(void) {
"-C : Change current working directory before "
"archiving/extracting\n");
fprintf(stderr,
- "--compressor : requires --decompressor\n");
+ "--compressor : requires --decompressor and cmd "
+ "must use stdin/stdout\n");
fprintf(stderr,
- "--decompressor : requires --compressor\n");
+ "--decompressor : requires --compressor and "
+ "cmd must use stdin/stdout\n");
fprintf(stderr,
" Specifying \"--decompressor\" when extracting overrides archive "
"file's stored decompressor cmd\n");