diff --git a/plugins/tpm/fu-tpm-device.c b/plugins/tpm/fu-tpm-device.c
index 05ad1ba54..8c31beb29 100644
--- a/plugins/tpm/fu-tpm-device.c
+++ b/plugins/tpm/fu-tpm-device.c
@@ -75,7 +75,7 @@ fu_tpm_device_get_string (ESYS_CONTEXT *ctx, guint32 query, GError **error)
 
 	/* convert non-ASCII into spaces */
 	for (guint i = 0; i < 4; i++) {
-		if (!g_ascii_isgraph (result[i]) && result[i] != '\0')
+		if (!g_ascii_isgraph (result[i]))
 			result[i] = 0x20;
 	}