diff --git a/nix/nixos-module/container/dhcp-server.nix b/nix/nixos-module/container/dhcp-server.nix
index 31c9cb9..29f566a 100644
--- a/nix/nixos-module/container/dhcp-server.nix
+++ b/nix/nixos-module/container/dhcp-server.nix
@@ -75,6 +75,10 @@ in
 
                 subnet ${subnet4Net} netmask ${lib.netmasks.${toString subnet4Len}} {
                   range ${dhcp.start} ${dhcp.end};
+
+                  # always assign the same IP to the same MAC address.
+                  # fixes changing IP for PXE clients.
+                  ignore-client-uids true;
                 }
 
                 update-static-leases on;