diff --git a/crates/lanspread-tauri-deno-ts/src/components/calltoplay/NominationCard.tsx b/crates/lanspread-tauri-deno-ts/src/components/calltoplay/NominationCard.tsx
index 834fdb9..2eff269 100644
--- a/crates/lanspread-tauri-deno-ts/src/components/calltoplay/NominationCard.tsx
+++ b/crates/lanspread-tauri-deno-ts/src/components/calltoplay/NominationCard.tsx
@@ -343,7 +343,10 @@ const CardActions = ({
                             if (accepted && game) onLaunch(game);
                         })}
                     ><Icon.play /><span>{game ? 'Start now' : 'Mark as running'}</span></button>
-                    <button className="ghost-btn" onClick={() => actions.addTime(nomination.id)}>
+                    <button
+                        className="ghost-btn"
+                        onClick={() => actions.addTime(nomination.id, nomination.deadline)}
+                    >
                         Add 5 more minutes
                     </button>
                 </>
diff --git a/crates/lanspread-tauri-deno-ts/src/hooks/useCallToPlay.ts b/crates/lanspread-tauri-deno-ts/src/hooks/useCallToPlay.ts
index 0e7e388..6e9f92a 100644
--- a/crates/lanspread-tauri-deno-ts/src/hooks/useCallToPlay.ts
+++ b/crates/lanspread-tauri-deno-ts/src/hooks/useCallToPlay.ts
@@ -4,6 +4,7 @@ import { listen, UnlistenFn } from '@tauri-apps/api/event';
 
 import {
     callToPlayEvent,
+    extendDeadline,
     pruneCallToPlayEvents,
     reduceCallToPlayEvents,
 } from '../lib/callToPlay';
@@ -22,7 +23,7 @@ export interface CallToPlayActions {
     leave: (callId: string) => void;
     cancel: (callId: string) => void;
     startNow: (callId: string) => Promise<boolean>;
-    addTime: (callId: string, minutes?: number) => void;
+    addTime: (callId: string, currentDeadline: number, minutes?: number) => void;
 }
 
 export interface UseCallToPlay {
@@ -175,8 +176,8 @@ export const useCallToPlay = (username: string): UseCallToPlay => {
         leave: callId => void publish(callId, 'Leave'),
         cancel: callId => void publish(callId, 'Cancel'),
         startNow: callId => publish(callId, 'Start'),
-        addTime: (callId, minutes = 5) => void publish(callId, {
-            AddTime: { deadline: Date.now() + minutes * 60_000 },
+        addTime: (callId, currentDeadline, minutes = 5) => void publish(callId, {
+            AddTime: { deadline: extendDeadline(Date.now(), currentDeadline, minutes) },
         }),
     }), [publish]);
 
diff --git a/crates/lanspread-tauri-deno-ts/src/lib/callToPlay.ts b/crates/lanspread-tauri-deno-ts/src/lib/callToPlay.ts
index 25d62bf..275a1f1 100644
--- a/crates/lanspread-tauri-deno-ts/src/lib/callToPlay.ts
+++ b/crates/lanspread-tauri-deno-ts/src/lib/callToPlay.ts
@@ -9,6 +9,12 @@ export const CHECKIN_LEAD_MS = 15 * 60_000;
 export const EXPIRED_RETENTION_MS = 5 * 60_000;
 export const TERMINAL_RETENTION_MS = 15 * 60_000;
 
+export const extendDeadline = (
+    now: number,
+    currentDeadline: number,
+    durationMinutes = 5,
+): number => Math.max(now, currentDeadline) + durationMinutes * 60_000;
+
 export type CallToPlayPhase = 'now' | 'scheduled' | 'checkin';
 export type CallToPlayStatus =
     | 'running'
diff --git a/crates/lanspread-tauri-deno-ts/tests/callToPlay.test.ts b/crates/lanspread-tauri-deno-ts/tests/callToPlay.test.ts
index 8cc21cc..025fe4c 100644
--- a/crates/lanspread-tauri-deno-ts/tests/callToPlay.test.ts
+++ b/crates/lanspread-tauri-deno-ts/tests/callToPlay.test.ts
@@ -3,6 +3,7 @@ import {
     EXPIRED_RETENTION_MS,
     TERMINAL_RETENTION_MS,
     activeCallCount,
+    extendDeadline,
     phaseOf,
     bumpTime,
     normalizeTimeInput,
@@ -163,6 +164,20 @@ Deno.test('creator can extend, start, and cancel a call', () => {
     assertEquals(cancelled.terminalAt, NOW + 1, 'cancel timestamp');
 });
 
+Deno.test('adding time extends from the current deadline or the current time', () => {
+    const futureDeadline = NOW + 30 * 60_000;
+    assertEquals(
+        extendDeadline(NOW, futureDeadline),
+        futureDeadline + 5 * 60_000,
+        'ready-early call keeps its remaining time',
+    );
+    assertEquals(
+        extendDeadline(NOW, NOW - 60_000),
+        NOW + 5 * 60_000,
+        'overdue call gets five minutes from now',
+    );
+});
+
 Deno.test('reduction is order-independent and deduplicates events and messages', () => {
     const message = event('message-event', 'Bob', {
         SendMessage: { message_id: 'message-1', text: 'Ready?' },