diff --git a/prototypes/ptth_quic_client_gui/src/main.rs b/prototypes/ptth_quic_client_gui/src/main.rs
index 077f60a..4dba9b9 100644
--- a/prototypes/ptth_quic_client_gui/src/main.rs
+++ b/prototypes/ptth_quic_client_gui/src/main.rs
@@ -136,7 +136,9 @@ impl GuiClient <'_> {
 		ports_col: &mut Flex,
 		fltk_tx: fltk::app::Sender <Message>
 	) {
-		if self.ports.len () >= 5 {
+		const MAX_PORTS: usize = 5;
+		
+		if self.ports.len () >= MAX_PORTS {
 			return;
 		}
 		
@@ -151,7 +153,7 @@ impl GuiClient <'_> {
 		
 		self.ports.push (port);
 		
-		if self.ports.len () >= 5 {
+		if self.ports.len () >= MAX_PORTS {
 			self.but_add_port.deactivate ();
 		}
 	}