diff --git a/share/man/man7/build.7 b/share/man/man7/build.7
index ca0d72e89c6..32c33aa3d73 100644
--- a/share/man/man7/build.7
+++ b/share/man/man7/build.7
@@ -500,6 +500,9 @@ The directory hierarchy prefix where built objects will be installed.
 If not set,
 .Va DESTDIR
 defaults to the empty string.
+If set,
+.Va DESTDIR
+must specify an absolute path.
 .It Va MAKEOBJDIRPREFIX
 Defines the prefix for directory names in the tree of built objects.
 Defaults to