diff --git a/libbacktrace/BacktraceThread.cpp b/libbacktrace/BacktraceThread.cpp
index 018d51f04..b47cd2ad2 100644
--- a/libbacktrace/BacktraceThread.cpp
+++ b/libbacktrace/BacktraceThread.cpp
@@ -117,6 +117,12 @@ void ThreadEntry::Wake() {
   futex(&futex_, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
 }
 
+void ThreadEntry::CopyUcontextFromSigcontext(void* sigcontext) {
+  ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(sigcontext);
+  // The only thing the unwinder cares about is the mcontext data.
+  memcpy(&ucontext_.uc_mcontext, &ucontext->uc_mcontext, sizeof(ucontext->uc_mcontext));
+}
+
 //-------------------------------------------------------------------------
 // BacktraceThread functions.
 //-------------------------------------------------------------------------
@@ -129,7 +135,7 @@ static void SignalHandler(int, siginfo_t*, void* sigcontext) {
     return;
   }
 
-  entry->CopyUcontext(reinterpret_cast<ucontext_t*>(sigcontext));
+  entry->CopyUcontextFromSigcontext(sigcontext);
 
   // Indicate the ucontext is now valid.
   entry->Wake();
diff --git a/libbacktrace/BacktraceThread.h b/libbacktrace/BacktraceThread.h
index a75a807be..ff3e9f3f4 100644
--- a/libbacktrace/BacktraceThread.h
+++ b/libbacktrace/BacktraceThread.h
@@ -40,14 +40,12 @@ public:
 
   static void Remove(ThreadEntry* entry);
 
-  inline void CopyUcontext(ucontext_t* ucontext) {
-    memcpy(&ucontext_, ucontext, sizeof(ucontext_));
-  }
-
   void Wake();
 
   void Wait(int);
 
+  void CopyUcontextFromSigcontext(void*);
+
   inline void Lock() {
     pthread_mutex_lock(&mutex_);
     // Reset the futex value in case of multiple unwinds of the same thread.