diff --git a/pigz.1 b/pigz.1
index 9315f16..a802541 100644
--- a/pigz.1
+++ b/pigz.1
@@ -116,7 +116,8 @@ indicates the slowest compression method (best compression).
 .B -0
 is no compression.
 .B \-11
-gives a few percent better compression at a severe cost in execution time.
+gives a few percent better compression at a severe cost in execution time,
+using the zopfli algorithm by Jyrki Alakuijala.
 The default is
 .B \-6.
 .TP
diff --git a/pigz.c b/pigz.c
index c0cc84b..458a755 100644
--- a/pigz.c
+++ b/pigz.c
@@ -3766,7 +3766,7 @@ local char *helptext[] = {
 #endif
 "",
 "Options:",
-"  -0 to -9, -11        Compression level (11 is much slower, a few % better)",
+"  -0 to -9, -11        Compression level (level 11, zopfli, is much slower)",
 "  --fast, --best       Compression levels 1 and 9 respectively",
 "  -b, --blocksize mmm  Set compression block size to mmmK (default 128K)",
 "  -c, --stdout         Write all processed output to stdout (won't delete)",
diff --git a/pigz.pdf b/pigz.pdf
index 6fbd1f0..118b884 100644
Binary files a/pigz.pdf and b/pigz.pdf differ