diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index f10e98aa5..4a97826f6 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -244,9 +244,11 @@ void ctr_drbg_entropy_usage(  )
     }
     TEST_ASSERT( last_idx == test_offset_idx );
 
-    /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT)
-     * (just make sure it doesn't cause memory corruption) */
-    mbedtls_ctr_drbg_update( &ctx, entropy, sizeof( entropy ) );
+    /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT).
+     * Make sure it's detected as an error and doesn't cause memory
+     * corruption. */
+    TEST_ASSERT( mbedtls_ctr_drbg_update_ret(
+                     &ctx, entropy, sizeof( entropy ) ) != 0 );
 
     /* Now enable PR, so the next few calls should all reseed */
     mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );