MbedTLS 3.6.1 using TLS 1.3

Mbed TLS
,
1

Hi, I’m using MbedTLS version 3.6.1 on a STM32 microcontroller(STM32H743II).
It works good when I only have support for TLS 1.2 enabled ( MBEDTLS_SSL_PROTO_TLS1_2).
But when I enable TLS 1.3 (MBEDTLS_SSL_PROTO_TLS1_3) the function mbedtls_ssl_handshake fails. When debugging I can see that

function entropy_gather_internal return MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED since
ctx->source_count == 0

Am I missing some init function or what might cause this behavior?

BR
Jonas