diff --git a/Lib/heapq.py b/Lib/heapq.py
index 00b429c..6cb22c3 100644
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -357,29 +357,36 @@ def merge(*iterables):
     [0, 1, 2, 3, 4, 5, 5, 7, 8, 10, 15, 20, 25]
 
     '''
-    _heappop, _heapreplace, _StopIteration = heappop, heapreplace, StopIteration
+    _heappop = heappop
+    _heapreplace = heapreplace
+    _StopIteration = StopIteration
+    _len = len
 
     h = []
     h_append = h.append
     for itnum, it in enumerate(map(iter, iterables)):
         try:
-            next = it.__next__
-            h_append([next(), itnum, next])
+            itnext = it.__next__
+            h_append([itnext(), itnum, itnext])
         except _StopIteration:
-            pass
-    heapify(h)
+            pass  # no items yielded at all
 
-    while 1:
+    heapify(h)
+    while _len(h) > 1:
         try:
-            while 1:
-                v, itnum, next = s = h[0]   # raises IndexError when h is empty
-                yield v
-                s[0] = next()               # raises StopIteration when exhausted
-                _heapreplace(h, s)          # restore heap condition
+            while True:
+                value, itnum, itnext = s = h[0]
+                yield value
+                s[0] = itnext()     # raises StopIteration when exhausted
+                _heapreplace(h, s)  # restore heap condition
         except _StopIteration:
-            _heappop(h)                     # remove empty iterator
-        except IndexError:
-            return
+            _heappop(h)             # remove empty iterator
+
+    if h:
+        # fast case when only a single iterator remains
+        value, itnum, itnext = h[0]
+        yield value
+        yield from itnext.__self__
 
 # Extend the implementations of nsmallest and nlargest to use a key= argument
 _nsmallest = nsmallest