diff --git a/tools/build/options/WITH_BEARSSL b/tools/build/options/WITH_BEARSSL
index 6a4447d723ed..9dcebbf1ae30 100644
--- a/tools/build/options/WITH_BEARSSL
+++ b/tools/build/options/WITH_BEARSSL
@@ -8,3 +8,22 @@ This library is currently only used to perform
 signature verification and related operations
 for Verified Exec and
 .Xr loader 8 .
+.Pp
+Due to size constraints, one may need to set
+.Va LOADERSIZE
+larger than the
+default 500000, although often loader is under the 500k limit even with
+this option.
+Setting
+.Va LOADERSIZE
+larger than 500000 may cause
+.Xr pxeboot 8
+to be too large to work.
+Careful testing of the loader in the target environment when built with a larger
+limit to establish safe limits is critical because different BIOS environments
+reserve differing amounts of the low 640k space, making a precise limit for
+everybody impossible.
+.Pp
+See also
+.Va WITH_LOADER_PXEBOOT
+for other considerations.
diff --git a/tools/build/options/WITH_LOADER_VERIEXEC b/tools/build/options/WITH_LOADER_VERIEXEC
index a50ff9a317e6..d784df968949 100644
--- a/tools/build/options/WITH_LOADER_VERIEXEC
+++ b/tools/build/options/WITH_LOADER_VERIEXEC
@@ -4,3 +4,5 @@ with support for verification similar to Verified Exec.
 .Pp
 Depends on
 .Va WITH_BEARSSL .
+May require a larger
+.Va LOADERSIZE .