diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index c9a95e1933..2338bebb84 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -1164,7 +1164,10 @@ static int ssl_tls13_write_certificate_verify_body( mbedtls_ssl_context *ssl,
 
     if( !mbedtls_ssl_sig_alg_is_received( ssl, algorithm ) )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        MBEDTLS_SSL_DEBUG_MSG( 1,
+                               ( "signature algorithm not in received list." ) );
+        MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
+                                      MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
         return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
     }
 
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index c61f2352fe..61c4407a66 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -9861,7 +9861,7 @@ run_test    "TLS 1.3: No client authentication, client has certificate - openssl
                     key_file=data_files/cli2.key" \
             0 \
             -c "got no certificate request" \
-            -C "client state: MBEDTLS_SSL_CLIENT_CERTIFICATE" \
+            -c "client state: MBEDTLS_SSL_CLIENT_CERTIFICATE" \
             -C "client state: MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY" \
             -c "Protocol is TLSv1.3"
 
@@ -9871,13 +9871,13 @@ requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_3
 requires_config_enabled MBEDTLS_DEBUG_C
 requires_config_enabled MBEDTLS_SSL_CLI_C
 requires_config_disabled MBEDTLS_USE_PSA_CRYPTO
-run_test    "TLS 1.3: No client authentication, client has certificate- gnutls" \
+run_test    "TLS 1.3: No client authentication, client has certificate - gnutls" \
             "$G_NEXT_SRV --disable-client-cert --debug=4 --priority=NORMAL:-VERS-ALL:+VERS-TLS1.3:+CIPHER-ALL:%NO_TICKETS:%DISABLE_TLS13_COMPAT_MODE" \
             "$P_CLI debug_level=3 min_version=tls13 max_version=tls13 crt_file=data_files/cli2.crt \
                     key_file=data_files/cli2.key" \
             0 \
             -c "got no certificate request" \
-            -C "client state: MBEDTLS_SSL_CLIENT_CERTIFICATE" \
+            -c "client state: MBEDTLS_SSL_CLIENT_CERTIFICATE" \
             -C "client state: MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY" \
             -c "Protocol is TLSv1.3"