Index: lib/Bitcode/Writer/ValueEnumerator.h
===================================================================
--- lib/Bitcode/Writer/ValueEnumerator.h
+++ lib/Bitcode/Writer/ValueEnumerator.h
@@ -94,7 +94,7 @@
     /// Number of strings in the prefix of the metadata range.
     unsigned NumStrings = 0;
 
-    MDRange() = default;
+    MDRange() {}
     explicit MDRange(unsigned First) : First(First) {}
   };
   SmallDenseMap<unsigned, MDRange, 1> FunctionMDInfo;