diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 041578e68..ec890d7dc 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -680,20 +680,20 @@ static void ssl_calc_finished_ssl( mbedtls_ssl_context *, unsigned char *, int )
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
-static void ssl_calc_verify_tls( const mbedtls_ssl_context *, unsigned char *, size_t * );
+static void ssl_calc_verify_tls( const mbedtls_ssl_context *, unsigned char [36], size_t * );
 static void ssl_calc_finished_tls( mbedtls_ssl_context *, unsigned char *, int );
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 #if defined(MBEDTLS_SHA256_C)
 static void ssl_update_checksum_sha256( mbedtls_ssl_context *, const unsigned char *, size_t );
-static void ssl_calc_verify_tls_sha256( const mbedtls_ssl_context *,unsigned char *, size_t * );
+static void ssl_calc_verify_tls_sha256( const mbedtls_ssl_context *,unsigned char [32], size_t * );
 static void ssl_calc_finished_tls_sha256( mbedtls_ssl_context *,unsigned char *, int );
 #endif
 
 #if defined(MBEDTLS_SHA512_C)
 static void ssl_update_checksum_sha384( mbedtls_ssl_context *, const unsigned char *, size_t );
-static void ssl_calc_verify_tls_sha384( const mbedtls_ssl_context *, unsigned char *, size_t * );
+static void ssl_calc_verify_tls_sha384( const mbedtls_ssl_context *, unsigned char [48], size_t * );
 static void ssl_calc_finished_tls_sha384( mbedtls_ssl_context *, unsigned char *, int );
 #endif
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */