diff --git a/man3/a64l.3 b/man3/a64l.3
index 61a1872f8..0a21f8218 100644
--- a/man3/a64l.3
+++ b/man3/a64l.3
@@ -12,7 +12,7 @@ a64l, l64a \- convert between long and base-64
 .SH SYNOPSIS
 .B #include <stdlib.h>
 .sp
-.BI "long a64l(char *" str64 );
+.BI "long a64l(const char *" str64 );
 .sp
 .BI "char *l64a(long " value );
 .sp