diff --git a/tests/qtest/bios-tables-test.c b/tests/qtest/bios-tables-test.c
index 71af5cf69f..fe6a9a8563 100644
--- a/tests/qtest/bios-tables-test.c
+++ b/tests/qtest/bios-tables-test.c
@@ -112,6 +112,7 @@ static const char *iasl;
 #endif
 
 static int verbosity_level;
+static GArray *load_expected_aml(test_data *data);
 
 static bool compare_signature(const AcpiSdtTable *sdt, const char *signature)
 {
@@ -244,21 +245,32 @@ static void test_acpi_fadt_table(test_data *data)
 
 static void dump_aml_files(test_data *data, bool rebuild)
 {
-    AcpiSdtTable *sdt;
+    AcpiSdtTable *sdt, *exp_sdt;
     GError *error = NULL;
     gchar *aml_file = NULL;
+    test_data exp_data = {};
     gint fd;
     ssize_t ret;
     int i;
 
+    exp_data.tables = load_expected_aml(data);
     for (i = 0; i < data->tables->len; ++i) {
         const char *ext = data->variant ? data->variant : "";
         sdt = &g_array_index(data->tables, AcpiSdtTable, i);
+        exp_sdt = &g_array_index(exp_data.tables, AcpiSdtTable, i);
         g_assert(sdt->aml);
+        g_assert(exp_sdt->aml);
 
         if (rebuild) {
             aml_file = g_strdup_printf("%s/%s/%.4s%s", data_dir, data->machine,
                                        sdt->aml, ext);
+            if (!g_file_test(aml_file, G_FILE_TEST_EXISTS) &&
+                sdt->aml_len == exp_sdt->aml_len &&
+                !memcmp(sdt->aml, exp_sdt->aml, sdt->aml_len)) {
+                /* identical tables, no need to write new files */
+                g_free(aml_file);
+                continue;
+            }
             fd = g_open(aml_file, O_WRONLY|O_TRUNC|O_CREAT,
                         S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH);
             if (fd < 0) {