diff --git a/bin/pgut/pgut.h b/bin/pgut/pgut.h
index 60a2a21..fd0d950 100755
--- a/bin/pgut/pgut.h
+++ b/bin/pgut/pgut.h
@@ -149,7 +149,8 @@ extern void CHECK_FOR_INTERRUPTS(void);
 #define appendStringInfoChar	appendPQExpBufferChar
 #define appendBinaryStringInfo	appendBinaryPQExpBuffer
 
-extern bool appendStringInfoVA(StringInfo str, const char *fmt, va_list args);
+extern bool appendStringInfoVA(StringInfo str, const char *fmt, va_list args)
+__attribute__((format(printf, 2, 0)));
 extern int appendStringInfoFile(StringInfo str, FILE *fp);
 extern int appendStringInfoFd(StringInfo str, int fd);
 
diff --git a/lib/pgut/pgut-spi.c b/lib/pgut/pgut-spi.c
index db117fe..daa661e 100755
--- a/lib/pgut/pgut-spi.c
+++ b/lib/pgut/pgut-spi.c
@@ -13,6 +13,10 @@
 #define EXEC_FAILED(ret, expected) \
 	(((expected) > 0 && (ret) != (expected)) || (ret) < 0)
 
+static void
+appendStringInfoVA_s(StringInfo str, const char *fmt, va_list args)
+__attribute__((format(printf, 2, 0)));
+
 static void
 termStringInfo(StringInfo str)
 {