diff --git a/django/db/models/query.py b/django/db/models/query.py
index 0f3a79a..817f518 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -104,7 +104,7 @@ class QuerySet(object):
             len(self)
 
         if self._result_cache is None:
-            self._iter = self.iterator()
+            self._iter = self.safe_iterator(self.iterator())
             self._result_cache = []
         if self._iter:
             return self._result_iter()
@@ -341,6 +341,18 @@ class QuerySet(object):
 
             yield obj
 
+    def safe_iterator(self, iterator):
+        # ensure result cache is cleared when iterating over a queryset
+        # raises an exception
+        try:
+            for item in iterator:
+                yield item
+        except StopIteration:
+            raise
+        except Exception:
+            self._result_cache = None
+            raise
+
     def aggregate(self, *args, **kwargs):
         """
         Returns a dictionary containing the calculations (aggregation)