diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index ea065095e5..aad93cbae7 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -1547,11 +1547,13 @@ void pk_rsa_decrypt_test_vec(data_t *cipher, int mod, int padding, int md_alg,
         TEST_ASSERT(olen == clear->len);
         TEST_ASSERT(memcmp(output, clear->x, olen) == 0);
 
-        /* Try again with an output buffer that's too small */
-        TEST_EQUAL(mbedtls_pk_decrypt(&pk, cipher->x, cipher->len,
-                                      output, &olen, clear->len - 1,
-                                      mbedtls_test_rnd_pseudo_rand, &rnd_info),
-                   MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE);
+        if (clear->len != 0) {
+            /* Try again with an output buffer that's too small */
+            TEST_EQUAL(mbedtls_pk_decrypt(&pk, cipher->x, cipher->len,
+                                          output, &olen, clear->len - 1,
+                                          mbedtls_test_rnd_pseudo_rand, &rnd_info),
+                       MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE);
+        }
     }
 
 exit:
@@ -1625,11 +1627,13 @@ void pk_wrap_rsa_decrypt_test_vec(data_t *cipher, int mod,
         TEST_EQUAL(olen, clear->len);
         TEST_EQUAL(memcmp(output, clear->x, olen), 0);
 
-        /* Try again with an output buffer that's too small */
-        TEST_EQUAL(mbedtls_pk_decrypt(&pk, cipher->x, cipher->len,
-                                      output, &olen, clear->len - 1,
-                                      mbedtls_test_rnd_pseudo_rand, &rnd_info),
-                   MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE);
+        if (clear->len != 0) {
+            /* Try again with an output buffer that's too small */
+            TEST_EQUAL(mbedtls_pk_decrypt(&pk, cipher->x, cipher->len,
+                                          output, &olen, clear->len - 1,
+                                          mbedtls_test_rnd_pseudo_rand, &rnd_info),
+                       MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE);
+        }
     }
 
     TEST_EQUAL(PSA_SUCCESS, psa_destroy_key(key_id));