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 <dir> : Change current working directory before archiving/extracting
-    --compressor <full_compress_cmd> : requires --decompressor
-    --decompressor <full_decompress_cmd> : requires --compressor
+    --compressor <full_compress_cmd> : requires --decompressor and cmd must use stdin/stdout
+    --decompressor <full_decompress_cmd> : 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 <dir> : Change current working directory before "
           "archiving/extracting\n");
   fprintf(stderr,
-          "--compressor <full_compress_cmd> : requires --decompressor\n");
+          "--compressor <full_compress_cmd> : requires --decompressor and cmd "
+          "must use stdin/stdout\n");
   fprintf(stderr,
-          "--decompressor <full_decompress_cmd> : requires --compressor\n");
+          "--decompressor <full_decompress_cmd> : requires --compressor and "
+          "cmd must use stdin/stdout\n");
   fprintf(stderr,
           "  Specifying \"--decompressor\" when extracting overrides archive "
           "file's stored decompressor cmd\n");