diff --git a/quic/test_tools/quic_test_utils.h b/quic/test_tools/quic_test_utils.h
index e10d9c1..17aa920 100644
--- a/quic/test_tools/quic_test_utils.h
+++ b/quic/test_tools/quic_test_utils.h
@@ -282,7 +282,7 @@
 
  private:
   uint8_t buffer_[4096];
-  size_t buffer_offset_;
+  size_t buffer_offset_ = 0;
   uint8_t key_[32];
 
   void FillBuffer();