diff --git a/lib/Support/FoldingSet.cpp b/lib/Support/FoldingSet.cpp
index 2d2279c..97d1f0d 100644
--- a/lib/Support/FoldingSet.cpp
+++ b/lib/Support/FoldingSet.cpp
@@ -326,7 +326,8 @@
 
 FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
   // Skip to the first non-null non-self-cycle bucket.
-  while (*Bucket == 0 || GetNextPtr(*Bucket) == 0)
+  while (*Bucket != reinterpret_cast<void*>(-1) &&
+         (*Bucket == 0 || GetNextPtr(*Bucket) == 0))
     ++Bucket;
   
   NodePtr = static_cast<FoldingSetNode*>(*Bucket);
@@ -345,7 +346,8 @@
     // Skip to the next non-null non-self-cycle bucket.
     do {
       ++Bucket;
-    } while (*Bucket == 0 || GetNextPtr(*Bucket) == 0);
+    } while (*Bucket != reinterpret_cast<void*>(-1) &&
+             (*Bucket == 0 || GetNextPtr(*Bucket) == 0));
     
     NodePtr = static_cast<FoldingSetNode*>(*Bucket);
   }