diff --git a/plugins/modem-manager/fu-firehose-updater.c b/plugins/modem-manager/fu-firehose-updater.c
index 61fd09bca..7d5a93128 100644
--- a/plugins/modem-manager/fu-firehose-updater.c
+++ b/plugins/modem-manager/fu-firehose-updater.c
@@ -691,9 +691,9 @@ fu_firehose_updater_run_action_program(FuFirehoseUpdater *self,
 	while ((payload_size + (guint)program_sector_size) <= max_payload_size)
 		payload_size += (guint)program_sector_size;
 
-	g_debug("sending program file '%s' (%zu bytes)",
+	g_debug("sending program file '%s' (0x%x bytes)",
 		program_filename,
-		g_bytes_get_size(program_file));
+		(guint)g_bytes_get_size(program_file));
 	if (!fu_firehose_updater_send_program_file(self,
 						   program_filename,
 						   program_file,