diff --git a/Lib/heapq.py b/Lib/heapq.py
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -358,6 +358,7 @@
 
     '''
     _heappop, _heapreplace, _StopIteration = heappop, heapreplace, StopIteration
+    _len = len
 
     h = []
     h_append = h.append
@@ -369,7 +370,7 @@
             pass
     heapify(h)
 
-    while 1:
+    while _len(h) > 1:
         try:
             while 1:
                 v, itnum, next = s = h[0]   # raises IndexError when h is empty
@@ -380,6 +381,11 @@
             _heappop(h)                     # remove empty iterator
         except IndexError:
             return
+    if h:
+        # fast case when only a single iterator remains
+        v, itnum, next = h[0]
+        yield v
+        yield from next.__self__
 
 # Extend the implementations of nsmallest and nlargest to use a key= argument
 _nsmallest = nsmallest