diff --git a/src/include/86box/timer.h b/src/include/86box/timer.h
index 4ade8aab0..91f903a0f 100644
--- a/src/include/86box/timer.h
+++ b/src/include/86box/timer.h
@@ -43,7 +43,7 @@ typedef struct pc_timer_t {
     ts_t ts;
 #endif
     int    flags;  /* The flags are defined above. */
-    int    pad;
+    int    in_callback;
     double period; /* This is used for large period timers to count
                       the microseconds and split the period. */
 
diff --git a/src/timer.c b/src/timer.c
index fa8376bde..d7102ffc3 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -94,6 +94,7 @@ timer_disable(pc_timer_t *timer)
         fatal("timer_disable - !timer->next\n");
 
     timer->flags &= ~TIMER_ENABLED;
+    timer->in_callback = 0;
 
     if (timer->prev)
         timer->prev->next = timer->next;
@@ -127,11 +128,15 @@ timer_process(void)
 
         if (timer->flags & TIMER_SPLIT)
             timer_advance_ex(timer, 0);   /* We're splitting a > 1 s period into
-                                             multiple <= 1 s periods. */
-        else if (timer->callback != NULL) /* Make sure it's not NULL, so that we can
-                                             have a NULL callback when no operation
-                                             is needed. */
+                                                 multiple <= 1 s periods. */
+        else if (timer->callback != NULL) {
+            /* Make sure it's not NULL, so that we can
+               have a NULL callback when no operation
+               is needed. */
+            timer->in_callback = 1;
             timer->callback(timer->priv);
+            timer->in_callback = 0;
+        }
     }
 
     timer_target = timer_head->ts.ts32.integer;
@@ -171,10 +176,11 @@ timer_add(pc_timer_t *timer, void (*callback)(void *priv), void *priv, int start
 {
     memset(timer, 0, sizeof(pc_timer_t));
 
-    timer->callback = callback;
-    timer->priv     = priv;
-    timer->flags    = 0;
-    timer->prev = timer->next = NULL;
+    timer->callback    = callback;
+    timer->in_callback = 0;
+    timer->priv        = priv;
+    timer->flags       = 0;
+    timer->prev        = timer->next = NULL;
     if (start_timer)
         timer_set_delay_u64(timer, 0);
 }
@@ -189,6 +195,7 @@ timer_stop(pc_timer_t *timer)
     timer->period = 0.0;
     timer_disable(timer);
     timer->flags &= ~TIMER_SPLIT;
+    timer->in_callback = 0;
 }
 
 static void
@@ -240,7 +247,9 @@ timer_on_auto(pc_timer_t *timer, double period)
         return;
 
     if (period > 0.0)
-        timer_on(timer, period, timer->period <= 0.0);
+        /* If the timer is in the callback, signal that, so that timer_advance_u64()
+           is used instead of timer_set_delay_u64(). */
+        timer_on(timer, period, (timer->period <= 0.0) && !timer->in_callback);
     else
         timer_stop(timer);
 }