diff --git a/lib/efi_selftest/efi_selftest_unicode_collation.c b/lib/efi_selftest/efi_selftest_unicode_collation.c
index c63a1b51e4e..11050a37cf7 100644
--- a/lib/efi_selftest/efi_selftest_unicode_collation.c
+++ b/lib/efi_selftest/efi_selftest_unicode_collation.c
@@ -184,6 +184,18 @@ static int test_fat_to_str(void)
 		return EFI_ST_FAILURE;
 	}
 
+	boottime->set_mem(str, sizeof(str), 0);
+	unicode_collation_protocol->fat_to_str(unicode_collation_protocol, 13,
+					       "Kafb\240tur\000xyz", str);
+	if (str[10]) {
+		efi_st_error("fat_to_str returned to many characters\n");
+		return EFI_ST_FAILURE;
+	}
+	if (efi_st_strcmp_16_8(str, "Kafb\341tur")) {
+		efi_st_error("fat_to_str returned \"%ps\"\n", str);
+		return EFI_ST_FAILURE;
+	}
+
 	return EFI_ST_SUCCESS;
 }