diff --git a/BL808Image.bt b/BL808Image.bt
index f82e45e9f7635f67bbb836b0e7451152044f5c53..2a52c04cbdcfb045efc945e75bdc30fd3d3100f3 100644
--- a/BL808Image.bt
+++ b/BL808Image.bt
@@ -231,7 +231,7 @@ if (BootHeader.magic != 0x504e4642)
     return 1;
 }
 
-if(BootHeader.flashCfgTableAddr < FileSize() && 
+if (BootHeader.flashCfgTableLen != 0 && BootHeader.flashCfgTableAddr < FileSize() &&
     BootHeader.flashCfgTableAddr + BootHeader.flashCfgTableLen <= FileSize()) {
     FSeek(BootHeader.flashCfgTableAddr);
     local quad num_configs = (BootHeader.flashCfgTableLen - 8) / 8;
@@ -268,7 +268,10 @@ if(BootHeader.flashCfgTableAddr < FileSize() &&
     }
     FSeek(off);
 } else {
-    Warning("flashCfgTable appears to either overlap with header, exist after the end of the file or overlap with the end of the file!");
+    // If flashCfgTableLen == 0, don't raise warning as it is allowed by this file format.
+    if (BootHeader.flashCfgTableLen != 0) {
+        Warning("flashCfgTable appears to either overlap with header, exist after the end of the file or overlap with the end of the file!");
+    }
 }
 
 if(BootHeader.basicCfg.img_len_cnt < FileSize() &&
@@ -279,21 +282,22 @@ if(BootHeader.basicCfg.img_len_cnt < FileSize() &&
     local int ret = ChecksumAlgStr(CHECKSUM_SHA256, s, startof(image),sizeof(image));
     if(ret) {
         local char ChecksumAlgStrResult[64 + 1];
-        for (i = 0; i < 8; i++) {
-            ChecksumAlgStrResult[i * 8 + 1] = (char)(BootHeader.basicCfg.hash[i] & 0xF);
-            ChecksumAlgStrResult[i * 8 + 0] = (char)((BootHeader.basicCfg.hash[i] >> 4) & 0xF);
-            ChecksumAlgStrResult[i * 8 + 3] = (char)((BootHeader.basicCfg.hash[i] >> 8) & 0xF);
-            ChecksumAlgStrResult[i * 8 + 2] = (char)((BootHeader.basicCfg.hash[i] >> 12) & 0xF);
-            ChecksumAlgStrResult[i * 8 + 5] = (char)((BootHeader.basicCfg.hash[i] >> 16) & 0xF);
-            ChecksumAlgStrResult[i * 8 + 4] = (char)((BootHeader.basicCfg.hash[i] >> 20) & 0xF);
-            ChecksumAlgStrResult[i * 8 + 7] = (char)((BootHeader.basicCfg.hash[i] >> 24) & 0xF);
-            ChecksumAlgStrResult[i * 8 + 6] = (char)((BootHeader.basicCfg.hash[i] >> 28) & 0xF);
+        local quad k;
+        for (k = 0; k < 8; k++) {
+            ChecksumAlgStrResult[k * 8 + 1] = (char)(BootHeader.basicCfg.hash[k] & 0xF);
+            ChecksumAlgStrResult[k * 8 + 0] = (char)((BootHeader.basicCfg.hash[k] >> 4) & 0xF);
+            ChecksumAlgStrResult[k * 8 + 3] = (char)((BootHeader.basicCfg.hash[k] >> 8) & 0xF);
+            ChecksumAlgStrResult[k * 8 + 2] = (char)((BootHeader.basicCfg.hash[k] >> 12) & 0xF);
+            ChecksumAlgStrResult[k * 8 + 5] = (char)((BootHeader.basicCfg.hash[k] >> 16) & 0xF);
+            ChecksumAlgStrResult[k * 8 + 4] = (char)((BootHeader.basicCfg.hash[k] >> 20) & 0xF);
+            ChecksumAlgStrResult[k * 8 + 7] = (char)((BootHeader.basicCfg.hash[k] >> 24) & 0xF);
+            ChecksumAlgStrResult[k * 8 + 6] = (char)((BootHeader.basicCfg.hash[k] >> 28) & 0xF);
         }
-        for (i = 0; i < 64; i++) {
-            if (ChecksumAlgStrResult[i] >= 10) {
-                ChecksumAlgStrResult[i] = ChecksumAlgStrResult[i] + 'A' - 10;
+        for (k = 0; k < 64; k++) {
+            if (ChecksumAlgStrResult[k] >= 10) {
+                ChecksumAlgStrResult[k] = ChecksumAlgStrResult[k] + 'A' - 10;
             } else {
-                ChecksumAlgStrResult[i] += '0';
+                ChecksumAlgStrResult[k] += '0';
             }
         }
         ChecksumAlgStrResult[64] = '\0';