diff --git a/LICENSE b/LICENSE
index 9feba16..9b802d2 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2014-2017 Armink (armink.ztl@gmail.com)
+Copyright (c) 2014-2018 Armink (armink.ztl@gmail.com)
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/easyflash/inc/easyflash.h b/easyflash/inc/easyflash.h
index 9848ff2..5a80585 100644
--- a/easyflash/inc/easyflash.h
+++ b/easyflash/inc/easyflash.h
@@ -1,7 +1,7 @@
 /*
  * This file is part of the EasyFlash Library.
  *
- * Copyright (c) 2014-2017, Armink, <armink.ztl@gmail.com>
+ * Copyright (c) 2014-2018, Armink, <armink.ztl@gmail.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -67,7 +67,7 @@ if (!(EXPR))                                                                  \
     while (1);                                                                \
 }
 /* EasyFlash software version number */
-#define EF_SW_VERSION                "3.0.3"
+#define EF_SW_VERSION                "3.0.4"
 
 typedef struct _ef_env{
     char *key;
diff --git a/easyflash/src/ef_env.c b/easyflash/src/ef_env.c
index 1383471..7407dc9 100644
--- a/easyflash/src/ef_env.c
+++ b/easyflash/src/ef_env.c
@@ -1,7 +1,7 @@
 /*
  * This file is part of the EasyFlash Library.
  *
- * Copyright (c) 2014-2016, Armink, <armink.ztl@gmail.com>
+ * Copyright (c) 2014-2018, Armink, <armink.ztl@gmail.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -246,7 +246,11 @@ static void set_env_end_addr(uint32_t end_addr) {
  * @return size
  */
 static size_t get_env_data_size(void) {
-    return get_env_end_addr() - get_env_data_addr();
+    if (get_env_end_addr() > get_env_data_addr()) {
+        return get_env_end_addr() - get_env_data_addr();
+    } else {
+        return 0;
+    }
 }
 
 /**
@@ -255,7 +259,11 @@ static size_t get_env_data_size(void) {
  * @return bytes
  */
 static size_t get_env_user_used_size(void) {
-    return get_env_end_addr() - get_env_system_addr();
+    if (get_env_end_addr() > get_env_system_addr()) {
+        return get_env_end_addr() - get_env_system_addr();
+    } else {
+        return 0;
+    }
 }
 
 /**
diff --git a/easyflash/src/ef_env_wl.c b/easyflash/src/ef_env_wl.c
index 7e1e01e..219e1be 100644
--- a/easyflash/src/ef_env_wl.c
+++ b/easyflash/src/ef_env_wl.c
@@ -1,7 +1,7 @@
 /*
  * This file is part of the EasyFlash Library.
  *
- * Copyright (c) 2015-2017, Armink, <armink.ztl@gmail.com>
+ * Copyright (c) 2015-2018, Armink, <armink.ztl@gmail.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -262,7 +262,11 @@ static void set_env_detail_end_addr(uint32_t end_addr) {
  * @return size
  */
 static size_t get_env_detail_size(void) {
-    return get_env_detail_end_addr() - get_env_detail_addr();
+    if (get_env_detail_end_addr() > get_env_detail_addr()) {
+        return get_env_detail_end_addr() - get_env_detail_addr();
+    } else {
+        return 0;
+    }
 }
 
 /**
@@ -274,7 +278,11 @@ static size_t get_env_detail_size(void) {
  */
     /* must be initialized */
 static size_t get_env_user_used_size(void) {
-    return get_env_detail_end_addr() - get_cur_using_data_addr();
+    if (get_env_detail_end_addr() > get_cur_using_data_addr()) {
+        return get_env_detail_end_addr() - get_cur_using_data_addr();
+    } else {
+        return 0;
+    }
 }
 
 /**