diff --git a/runtime/utils.cc b/runtime/utils.cc
index 13564a6..472a85c 100644
--- a/runtime/utils.cc
+++ b/runtime/utils.cc
@@ -1120,7 +1120,8 @@
   }
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(BACKTRACE_CURRENT_PROCESS, tid, map));
   if (!backtrace->Unwind(0, reinterpret_cast<ucontext*>(ucontext_ptr))) {
-    os << prefix << "(backtrace::Unwind failed for thread " << tid << ")\n";
+    os << prefix << "(backtrace::Unwind failed for thread " << tid
+       << ": " <<  backtrace->GetErrorString(backtrace->GetError()) << ")\n";
     return;
   } else if (backtrace->NumFrames() == 0) {
     os << prefix << "(no native stack frames for thread " << tid << ")\n";