diff --git a/tests/suites/test_suite_cipher.function b/tests/suites/test_suite_cipher.function
index 47a763c..ffe3284 100644
--- a/tests/suites/test_suite_cipher.function
+++ b/tests/suites/test_suite_cipher.function
@@ -1155,6 +1155,16 @@
     unsigned char *tag_buf = NULL;
 #endif /* !MBEDTLS_DEPRECATED_WARNING && !MBEDTLS_DEPRECATED_REMOVED */
 
+    /* Null pointers are documented as valid for inputs of length 0.
+     * The test framework passes non-null pointers, so set them to NULL.
+     * key, cipher and tag can't be empty. */
+    if( iv->len == 0 )
+        iv->x = NULL;
+    if( ad->len == 0 )
+        ad->x = NULL;
+    if( clear->len == 0 )
+        clear->x = NULL;
+
     mbedtls_cipher_init( &ctx );
 
     /* Initialize PSA Crypto */
@@ -1345,8 +1355,7 @@
      * Authenticate and decrypt, and check result
      */
 
-    /* We can't pass a NULL output buffer to this function */
-    ASSERT_ALLOC( decrypt_buf, cipher->len ? cipher->len : 1 );
+    ASSERT_ALLOC( decrypt_buf, cipher->len );
     outlen = 0;
     ret = mbedtls_cipher_auth_decrypt( &ctx, iv->x, iv->len, ad->x, ad->len,
                                tmp_cipher, cipher->len, decrypt_buf, &outlen,
@@ -1397,8 +1406,7 @@
         else
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
         {
-            /* can't pass a NULL output buffer to this function */
-            ASSERT_ALLOC( encrypt_buf, cipher->len ? cipher->len : 1 );
+            ASSERT_ALLOC( encrypt_buf, cipher->len );
             ASSERT_ALLOC( tag_buf, tag->len );
             tmp_cipher = encrypt_buf;
             tmp_tag = tag_buf;
@@ -1421,7 +1429,8 @@
             TEST_ASSERT( ret == 0 );
 
             TEST_ASSERT( outlen == cipher->len );
-            TEST_ASSERT( memcmp( tmp_cipher, cipher->x, cipher->len ) == 0 );
+            if( cipher->len != 0 )
+                TEST_ASSERT( memcmp( tmp_cipher, cipher->x, cipher->len ) == 0 );
             TEST_ASSERT( memcmp( tmp_tag, tag->x, tag->len ) == 0 );
         }
     }