diff --git a/llvm/include/llvm/MC/MCContext.h b/llvm/include/llvm/MC/MCContext.h
--- a/llvm/include/llvm/MC/MCContext.h
+++ b/llvm/include/llvm/MC/MCContext.h
@@ -190,7 +190,7 @@
   SmallString<128> CompilationDir;
 
   /// Prefix replacement map for source file information.
-  std::map<const std::string, const std::string> DebugPrefixMap;
+  std::map<const std::string, const std::string, std::greater<std::string>> DebugPrefixMap;
 
   /// The main file name if passed in explicitly.
   std::string MainFileName;