diff --git a/ch10-iterators/e49b1_elapsed_since_wait.py b/ch10-iterators/e49b1_elapsed_since_wait.py
index 8605482..e5c2f0b 100755
--- a/ch10-iterators/e49b1_elapsed_since_wait.py
+++ b/ch10-iterators/e49b1_elapsed_since_wait.py
@@ -13,6 +13,8 @@ def elapsed_since(data, min_wait):
 
         if delta < min_wait:
             time.sleep(min_wait - delta)
+            current_time = time.perf_counter()
+            delta = current_time - (last_time or current_time)
 
         last_time = time.perf_counter()
         yield (delta, item)