diff --git a/ui/validate.func b/ui/validate.func
index 983bdd5..39ac0f0 100644
--- a/ui/validate.func
+++ b/ui/validate.func
@@ -402,6 +402,9 @@ validate_gateway_in_subnet() {
   local ip="${static_ip%%/*}"
   local cidr="${static_ip##*/}"
 
+  # /31 and /32 have no usable subnet, so an off-subnet gateway is normal there.
+  ((cidr >= 31)) && return 0
+
   # Convert CIDR to netmask bits
   local mask=$((0xFFFFFFFF << (32 - cidr) & 0xFFFFFFFF))