diff --git a/lib/mammoth/include/mammoth/thread.h b/lib/mammoth/include/mammoth/thread.h
index 5597848..804db35 100644
--- a/lib/mammoth/include/mammoth/thread.h
+++ b/lib/mammoth/include/mammoth/thread.h
@@ -6,6 +6,7 @@ class Thread {
  public:
   typedef void (*Entry)(void*);
 
+  Thread() : thread_cap_(0) {}
   Thread(Entry e, const void* arg1);
 
  private: