diff --git a/library/ssl_ticket.c b/library/ssl_ticket.c
index 9767783..ce4607e 100644
--- a/library/ssl_ticket.c
+++ b/library/ssl_ticket.c
@@ -162,7 +162,7 @@
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
-    const int bitlen = key->key_bits;
+    const size_t bitlen = key->key_bits;
 #else
     const int bitlen = mbedtls_cipher_get_key_bitlen( &key->ctx );
 #endif