diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index e847836..b8b222b 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -270,6 +270,8 @@
 
     TEST_ASSERT( mbedtls_pk_sign( &pk, MBEDTLS_MD_SHA256, hash, sizeof hash,
                           sig, &sig_len, rnd_std_rand, NULL ) == sign_ret );
+    if( sign_ret == 0 )
+        TEST_ASSERT( sig_len <= mbedtls_pk_signature_size( &pk ) );
 
     TEST_ASSERT( mbedtls_pk_verify( &pk, MBEDTLS_MD_SHA256,
                             hash, sizeof hash, sig, sig_len ) == verify_ret );