diff --git a/libbacktrace/UnwindPtrace.h b/libbacktrace/UnwindPtrace.h
index 1e82117..2fb7967 100644
--- a/libbacktrace/UnwindPtrace.h
+++ b/libbacktrace/UnwindPtrace.h
@@ -28,7 +28,7 @@
   UnwindPtrace();
   virtual ~UnwindPtrace();
 
-  virtual bool Unwind(size_t num_ignore_frames);
+  virtual bool Unwind(size_t num_ignore_frames, ucontext_t* ucontext);
 
   virtual std::string GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset);