diff --git a/src/diag_io.c b/src/diag_io.c
index 36f92dc..b8dd18b 100644
--- a/src/diag_io.c
+++ b/src/diag_io.c
@@ -31,7 +31,7 @@
 
 	rc = write(di->fd, packet, out_len);
 	if (rc != out_len) {
-		printf("Short write on packet.\n");
+		fprintf(stderr, "Short write on packet.\n");
 		return -1;
 	}