diff --git a/library/lms.c b/library/lms.c
index a8411797d..1e0f31910 100644
--- a/library/lms.c
+++ b/library/lms.c
@@ -733,7 +733,7 @@ int mbedtls_lms_sign( mbedtls_lms_private_t *ctx,
     ret = mbedtls_lmots_sign( &ctx->ots_private_keys[q_leaf_identifier],
                               f_rng, p_rng, msg, msg_size,
                               sig + SIG_OTS_SIG_OFFSET,
-                              MBEDTLS_LMS_SIG_LEN(ctx->params.type, ctx->params.otstype),
+                              MBEDTLS_LMS_SIG_LEN(ctx->params.type, ctx->params.otstype) - SIG_OTS_SIG_OFFSET,
                               NULL );
     if( ret != 0 )
     {