diff --git a/lib/libc/stdlib/getsubopt.3 b/lib/libc/stdlib/getsubopt.3
index 3f6f547ce19..8a0c3e09698 100644
--- a/lib/libc/stdlib/getsubopt.3
+++ b/lib/libc/stdlib/getsubopt.3
@@ -38,7 +38,7 @@
 .Nm getsubopt
 .Nd get sub options from an argument
 .Sh SYNOPSIS
-.Fd #include <stdlib.h>
+.Fd #include <unistd.h>
 .Vt extern char *suboptarg
 .Ft int
 .Fn getsubopt "char **optionp" "char * const *tokens" "char **valuep"