diff --git a/lldb/include/lldb/Core/Timer.h b/lldb/include/lldb/Core/Timer.h
index 46202e2e61e1..8bc68cf54e36 100644
--- a/lldb/include/lldb/Core/Timer.h
+++ b/lldb/include/lldb/Core/Timer.h
@@ -11,6 +11,7 @@
 #define liblldb_Timer_h_
 #if defined(__cplusplus)
 
+#include <stdarg.h>
 #include <stdio.h>
 #include <memory>
 #include <string>