diff --git a/cmirror.c b/cmirror.c
index 1e1f5d5..5e6b97b 100644
--- a/cmirror.c
+++ b/cmirror.c
@@ -36,7 +36,7 @@
 static const char *log_prefix;
 static int noisy_abort;
 
-static void warn(const char *restrict fmt, ...) {
+static G_GNUC_PRINTF(1, 2) void warn(const char *restrict fmt, ...) {
     if (log_prefix)
         fprintf(stderr, "%s: ", log_prefix);
     va_list ap;
@@ -45,7 +45,7 @@ static void warn(const char *restrict fmt, ...) {
     va_end(ap);
 }
 
-static G_NORETURN void die(const char *restrict fmt, ...) {
+static G_NORETURN G_GNUC_PRINTF(1, 2) void die(const char *restrict fmt, ...) {
     if (fmt) {
         if (log_prefix)
             fprintf(stderr, "%s: ", log_prefix);