diff --git a/library/pk_wrap.h b/library/pk_wrap.h
index b2db637..42ccca7 100644
--- a/library/pk_wrap.h
+++ b/library/pk_wrap.h
@@ -53,7 +53,7 @@
     /** Make signature */
     int (*sign_func)( void *ctx, mbedtls_md_type_t md_alg,
                       const unsigned char *hash, size_t hash_len,
-                      unsigned char *sig, size_t *sig_len,
+                      unsigned char *sig, size_t sig_size, size_t *sig_len,
                       int (*f_rng)(void *, unsigned char *, size_t),
                       void *p_rng );
 
@@ -67,7 +67,7 @@
     /** Make signature (restartable) */
     int (*sign_rs_func)( void *ctx, mbedtls_md_type_t md_alg,
                          const unsigned char *hash, size_t hash_len,
-                         unsigned char *sig, size_t *sig_len,
+                         unsigned char *sig, size_t sig_size, size_t *sig_len,
                          int (*f_rng)(void *, unsigned char *, size_t),
                          void *p_rng, void *rs_ctx );
 #endif /* MBEDTLS_ECDSA_C && MBEDTLS_ECP_RESTARTABLE */