diff --git a/format_test.cc b/format_test.cc
index 91b5fe73..016687e1 100644
--- a/format_test.cc
+++ b/format_test.cc
@@ -38,6 +38,7 @@
 // Check if format.h compiles with windows.h included.
 #ifdef _WIN32
 # include <windows.h>
+# include <crtdbg.h>
 #endif
 
 #include "format.h"