diff --git a/SheepShaver/src/Unix/sysdeps.h b/SheepShaver/src/Unix/sysdeps.h
index d7e51b68..ead34d50 100644
--- a/SheepShaver/src/Unix/sysdeps.h
+++ b/SheepShaver/src/Unix/sysdeps.h
@@ -419,7 +419,7 @@ typedef struct timeval tm_time_t;
 #define C4X_FLOAT_FORMAT 4
 
 // High-precision timing
-#if defined(HAVE_PTHREADS) && defined(HAVE_CLOCK_NANOSLEEP) && 0
+#if defined(HAVE_PTHREADS) && defined(HAVE_CLOCK_NANOSLEEP)
 #define PRECISE_TIMING 1
 #define PRECISE_TIMING_POSIX 1
 #endif
diff --git a/SheepShaver/src/timer.cpp b/SheepShaver/src/timer.cpp
index 30a9e77e..526272e6 100644
--- a/SheepShaver/src/timer.cpp
+++ b/SheepShaver/src/timer.cpp
@@ -532,15 +532,15 @@ static void *timer_func(void *arg)
 
 		tm_time_t system_time;
 		timer_current_time(system_time);
-		pthread_mutex_lock(&wakeup_time_lock);
 		if (timer_cmp_time(wakeup_time, system_time) < 0) {
 
 			// Timer expired, trigger interrupt
+			pthread_mutex_lock(&wakeup_time_lock);
 			wakeup_time = wakeup_time_max;
+			pthread_mutex_unlock(&wakeup_time_lock);
 			SetInterruptFlag(INTFLAG_TIMER);
 			TriggerInterrupt();
 		}
-		pthread_mutex_unlock(&wakeup_time_lock);
 	}
 	return NULL;
 }