diff --git a/include/qapi/error.h b/include/qapi/error.h
index 7932594dce..eaa05c4837 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -382,13 +382,15 @@ void error_propagate(Error **dst_errp, Error *local_err);
  * Please use ERRP_GUARD() and error_prepend() instead when possible.
  */
 void error_propagate_prepend(Error **dst_errp, Error *local_err,
-                             const char *fmt, ...);
+                             const char *fmt, ...)
+    GCC_FMT_ATTR(3, 4);
 
 /*
  * Prepend some text to @errp's human-readable error message.
  * The text is made by formatting @fmt, @ap like vprintf().
  */
-void error_vprepend(Error *const *errp, const char *fmt, va_list ap);
+void error_vprepend(Error *const *errp, const char *fmt, va_list ap)
+    GCC_FMT_ATTR(2, 0);
 
 /*
  * Prepend some text to @errp's human-readable error message.