diff --git a/tests/suites/test_suite_ccm.function b/tests/suites/test_suite_ccm.function
index f597c6914..d8ca4f5d1 100644
--- a/tests/suites/test_suite_ccm.function
+++ b/tests/suites/test_suite_ccm.function
@@ -146,6 +146,7 @@ void ccm_auth_decrypt( int cipher_id,
     if( strcmp( "FAIL", result_hex ) == 0 )
     {
         ret = POLARSSL_ERR_CCM_AUTH_FAILED;
+        result_len = -1;
     }
     else
     {