diff --git a/gnu/usr.bin/diff/diff.1 b/gnu/usr.bin/diff/diff.1
index 83b79913862..0164f232d25 100644
--- a/gnu/usr.bin/diff/diff.1
+++ b/gnu/usr.bin/diff/diff.1
@@ -317,6 +317,9 @@ Use
 to output a line taken from just the first file in
 if-then-else format.
 .TP
+.B \-p
+Show which C function each change is in.
+.TP
 .B \-P
 When comparing directories, if a file appears only in the second
 directory of the two, treat it as present but empty in the other.