Index: lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- lib/Bitcode/Reader/BitcodeReader.cpp
+++ lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3113,8 +3113,8 @@
     case bitc::IDENTIFICATION_CODE_EPOCH: { // EPOCH:      [epoch#]
       unsigned epoch = (unsigned)Record[0];
       if (epoch != bitc::BITCODE_CURRENT_EPOCH) {
-        auto BitcodeEpoch = std::to_string(epoch);
-        auto CurrentEpoch = std::to_string(bitc::BITCODE_CURRENT_EPOCH);
+        auto BitcodeEpoch = Twine(epoch);
+        auto CurrentEpoch = Twine(bitc::BITCODE_CURRENT_EPOCH);
         return error(Twine("Incompatible epoch: Bitcode '") + BitcodeEpoch +
                      "' vs current: '" + CurrentEpoch + "'");
       }