diff --git a/library/debug.c b/library/debug.c
index c3384be..e91d1ad 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -74,6 +74,7 @@
 #endif
 }
 
+MBEDTLS_PRINTF_ATTRIBUTE(5, 6)
 void mbedtls_debug_print_msg( const mbedtls_ssl_context *ssl, int level,
                               const char *file, int line,
                               const char *format, ... )