diff --git a/include/rabit/rabit-inl.h b/include/rabit/rabit-inl.h
index 97c43767d..94da54a2f 100644
--- a/include/rabit/rabit-inl.h
+++ b/include/rabit/rabit-inl.h
@@ -174,6 +174,7 @@ inline void TrackerPrintf(const char *fmt, ...) {
   va_start(args, fmt);
   vsnprintf(&msg[0], kPrintBuffer, fmt, args);
   va_end(args);
+  msg.resize(strlen(msg.c_str());
   TrackerPrint(msg);
 }
 #endif