diff --git a/tests/pthread_test.cpp b/tests/pthread_test.cpp
index 749d687..1a882be 100644
--- a/tests/pthread_test.cpp
+++ b/tests/pthread_test.cpp
@@ -2398,6 +2398,20 @@
   ts.tv_sec = -1;
   ASSERT_EQ(ETIMEDOUT, lock_function(&m, &ts));
 
+  // check we wait long enough for the lock.
+  ASSERT_EQ(0, clock_gettime(clock, &ts));
+  const int64_t start_ns = ts.tv_sec * NS_PER_S + ts.tv_nsec;
+
+  // add a second to get deadline.
+  ts.tv_sec += 1;
+
+  ASSERT_EQ(ETIMEDOUT, lock_function(&m, &ts));
+
+  // The timedlock must have waited at least 1 second before returning.
+  clock_gettime(clock, &ts);
+  const int64_t end_ns = ts.tv_sec * NS_PER_S + ts.tv_nsec;
+  ASSERT_GT(end_ns - start_ns, NS_PER_S);
+
   // If the mutex is unlocked, pthread_mutex_timedlock should succeed.
   ASSERT_EQ(0, pthread_mutex_unlock(&m));
 
@@ -2443,7 +2457,11 @@
 
   timespec ts;
   clock_gettime(clock, &ts);
+  const int64_t start_ns = ts.tv_sec * NS_PER_S + ts.tv_nsec;
+
+  // add a second to get deadline.
   ts.tv_sec += 1;
+
   ASSERT_EQ(0, lock_function(&m.lock, &ts));
 
   struct ThreadArgs {
@@ -2472,6 +2490,12 @@
   void* result;
   ASSERT_EQ(0, pthread_join(thread, &result));
   ASSERT_EQ(ETIMEDOUT, reinterpret_cast<intptr_t>(result));
+
+  // The timedlock must have waited at least 1 second before returning.
+  clock_gettime(clock, &ts);
+  const int64_t end_ns = ts.tv_sec * NS_PER_S + ts.tv_nsec;
+  ASSERT_GT(end_ns - start_ns, NS_PER_S);
+
   ASSERT_EQ(0, pthread_mutex_unlock(&m.lock));
 }