diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 96e0e06bbbf0..ae22295df798 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -307,7 +307,7 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 		out = (struct tpm2_get_random_out *)&buf->data[offset];
 		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
 		if (tpm_buf_length(buf) <
-		    TPM_HEADER_SIZE +
+		    offset +
 		    offsetof(struct tpm2_get_random_out, buffer) +
 		    recd) {
 			tpm2_end_auth_session(chip);