1 files changed, 3 insertions, 0 deletions
diff --git a/include/clang/Serialization/ContinuousRangeMap.h b/include/clang/Serialization/ContinuousRangeMap.h
index 42b8954b54..7f78320410 100644
--- a/include/clang/Serialization/ContinuousRangeMap.h
+++ b/include/clang/Serialization/ContinuousRangeMap.h
@@ -61,6 +61,9 @@ private:
 
 public:
   void insert(const value_type &Val) {
+    if (!Rep.empty() && Rep.back() == Val)
+      return;
+
     assert((Rep.empty() || Rep.back().first < Val.first) &&
            "Must insert keys in order.");
     Rep.push_back(Val);