diff --git a/src/hardware/baylibre-acme/protocol.c b/src/hardware/baylibre-acme/protocol.c
index 66a22ad4..e7f1ede1 100644
--- a/src/hardware/baylibre-acme/protocol.c
+++ b/src/hardware/baylibre-acme/protocol.c
@@ -334,7 +334,7 @@ SR_PRIV int bl_acme_set_shunt(const struct sr_channel_group *cg, uint64_t shunt)
 	}
 
 	g_string_free(path, TRUE);
-	g_fprintf(fd, "%llu\n", MOHM_TO_UOHM(shunt));
+	g_fprintf(fd, "%" PRIu64 "\n", MOHM_TO_UOHM(shunt));
 	/*
 	 * XXX There's no g_fclose() in GLib. This seems to work,
 	 * but is it safe?