--- a/triggers/stringutil.c
+++ b/triggers/stringutil.c
@@ -23,6 +23,9 @@
 #if PG_VERSION_NUM >= 90200
 #include <utils/json.h>
 #endif
+#if PG_VERSION_NUM >= 160000
+#include <varatt.h>
+#endif
 
 #include "stringutil.h"
 
