1 files changed, 1 insertions, 0 deletions
diff --git a/src/tac.c b/src/tac.c
index 7b06de715..2b0a2d8be 100644
--- a/src/tac.c
+++ b/src/tac.c
@@ -132,6 +132,7 @@ Usage: %s [OPTION]... [FILE]...\n\
 Write each FILE to standard output, last line first.\n\
 With no FILE, or when FILE is -, read standard input.\n\
 \n\
+Mandatory arguments to long options are mandatory for short options too.\n\
   -b, --before             attach the separator before instead of after\n\
   -r, --regex              interpret the separator as a regular expression\n\
   -s, --separator=STRING   use STRING as the separator instead of newline\n\