diff --git a/quic/core/quic_time.cc b/quic/core/quic_time.cc
index 92a3eec..e3df0b9 100644
--- a/quic/core/quic_time.cc
+++ b/quic/core/quic_time.cc
@@ -13,7 +13,7 @@
 
 namespace quic {
 
-QuicString QuicTime::Delta::ToDebugValue() const {
+std::string QuicTime::Delta::ToDebugValue() const {
   const int64_t one_ms = 1000;
   const int64_t one_s = 1000 * one_ms;