diff --git a/include/llvm/ADT/StringMap.h b/include/llvm/ADT/StringMap.h
index f3d6b9f4849..907c72d685e 100644
--- a/include/llvm/ADT/StringMap.h
+++ b/include/llvm/ADT/StringMap.h
@@ -329,6 +329,7 @@ public:
       --NumTombstones;
     Bucket.Item = KeyValue;
     ++NumItems;
+    assert(NumItems + NumTombstones <= NumBuckets);
 
     RehashTable();
     return true;
@@ -348,6 +349,7 @@ public:
     }
 
     NumItems = 0;
+    NumTombstones = 0;
   }
 
   /// GetOrCreateValue - Look up the specified key in the table.  If a value
@@ -367,6 +369,7 @@ public:
     if (Bucket.Item == getTombstoneVal())
       --NumTombstones;
     ++NumItems;
+    assert(NumItems + NumTombstones <= NumBuckets);
 
     // Fill in the bucket for the hash table.  The FullHashValue was already
     // filled in by LookupBucketFor.
diff --git a/lib/Support/StringMap.cpp b/lib/Support/StringMap.cpp
index f193aa42a44..a1ac512fa24 100644
--- a/lib/Support/StringMap.cpp
+++ b/lib/Support/StringMap.cpp
@@ -169,6 +169,8 @@ StringMapEntryBase *StringMapImpl::RemoveKey(StringRef Key) {
   TheTable[Bucket].Item = getTombstoneVal();
   --NumItems;
   ++NumTombstones;
+  assert(NumItems + NumTombstones <= NumBuckets);
+
   return Result;
 }
 
@@ -224,4 +226,5 @@ void StringMapImpl::RehashTable() {
   
   TheTable = NewTableArray;
   NumBuckets = NewSize;
+  NumTombstones = 0;
 }