diff --git a/sw/device/sca/aes_serial.c b/sw/device/sca/aes_serial.c
index d56a4133fc4dd4..b1971fcb5abeb2 100644
--- a/sw/device/sca/aes_serial.c
+++ b/sw/device/sca/aes_serial.c
@@ -775,8 +775,13 @@ bool test_main(void) {
     LOG_INFO("Initializing entropy complex.");
     CHECK_STATUS_OK(aes_testutils_masking_prng_zero_output_seed());
     CHECK_DIF_OK(dif_aes_trigger(&aes, kDifAesTriggerPrngReseed));
+    bool idle = false;
+    do {
+      CHECK_DIF_OK(dif_aes_get_status(&aes, kDifAesStatusIdle, &idle));
+    } while (!idle);
   }
 #endif
+  CHECK_DIF_OK(dif_aes_trigger(&aes, kDifAesTriggerDataOutClear));
 
   LOG_INFO("Starting simple serial packet handling.");
   while (true) {
diff --git a/sw/device/tests/aes_masking_off_test.c b/sw/device/tests/aes_masking_off_test.c
index 1363a886b33a8d..320c3f1e625c1b 100644
--- a/sw/device/tests/aes_masking_off_test.c
+++ b/sw/device/tests/aes_masking_off_test.c
@@ -93,6 +93,11 @@ status_t execute_test(void) {
   CHECK_DIF_OK(dif_aes_trigger(&aes, kDifAesTriggerPrngReseed));
   AES_TESTUTILS_WAIT_FOR_STATUS(&aes, kDifAesStatusIdle, true, kTestTimeout);
 
+  // Trigger the clearing of the output data registers. After this point, also
+  // the PRNG buffer stage will output an all-zero vector.
+  CHECK_DIF_OK(dif_aes_trigger(&aes, kDifAesTriggerDataOutClear));
+  AES_TESTUTILS_WAIT_FOR_STATUS(&aes, kDifAesStatusIdle, true, kTestTimeout);
+
   // "Convert" plain data byte arrays to `dif_aes_data_t` array.
   enum {
     kAesNumBlocks = 4,