diff --git a/codec/decoder/core/inc/error_code.h b/codec/decoder/core/inc/error_code.h
index 2ce2b0eb..4fbd9258 100644
--- a/codec/decoder/core/inc/error_code.h
+++ b/codec/decoder/core/inc/error_code.h
@@ -184,6 +184,7 @@ ERR_INFO_NO_IDR_PIC             = ERR_INFO_LOGIC_BASE,  // NO IDR picture availa
 ERR_INFO_EC_NO_NEIGHBOUR_MBS,
 ERR_INFO_EC_UNEXPECTED_MB_TYPE,
 ERR_INFO_EC_NO_ENOUGH_NEIGHBOUR_MBS,
+ERR_INFO_DUPLICATE_FRAME_NUM,
 //for LTR
 ERR_INFO_INVALID_MMCO_OPCODE_BASE,
 ERR_INFO_INVALID_MMCO_SHORT2UNUSED,
diff --git a/codec/decoder/core/src/decoder_core.cpp b/codec/decoder/core/src/decoder_core.cpp
index 3b6a794b..4be9be50 100644
--- a/codec/decoder/core/src/decoder_core.cpp
+++ b/codec/decoder/core/src/decoder_core.cpp
@@ -2360,6 +2360,8 @@ int32_t DecodeCurrentAccessUnit (PWelsDecoderContext pCtx, uint8_t** ppDst, SBuf
       if (uiNalRefIdc > 0) {
         iRet = WelsMarkAsRef (pCtx);
         if (iRet != ERR_NONE) {
+          if (iRet == ERR_INFO_DUPLICATE_FRAME_NUM)
+            pCtx->iErrorCode |= dsBitstreamError;
           if (pCtx->eErrorConMethod == ERROR_CON_DISABLE) {
             pCtx->pDec = NULL;
             return iRet;
diff --git a/codec/decoder/core/src/error_concealment.cpp b/codec/decoder/core/src/error_concealment.cpp
index ab0b3576..345cf287 100644
--- a/codec/decoder/core/src/error_concealment.cpp
+++ b/codec/decoder/core/src/error_concealment.cpp
@@ -431,6 +431,7 @@ void DoErrorConSliceMVCopy (PWelsDecoderContext pCtx) {
 //Mark erroneous frame as Ref Pic into DPB
 int32_t MarkECFrameAsRef (PWelsDecoderContext pCtx) {
   int32_t iRet = WelsMarkAsRef (pCtx);
+  // Under EC mode, the ERR_INFO_DUPLICATE_FRAME_NUM does not need to be process
   if (iRet != ERR_NONE) {
     return iRet;
   }
diff --git a/codec/decoder/core/src/manage_dec_ref.cpp b/codec/decoder/core/src/manage_dec_ref.cpp
index fe9366d8..fec60b7b 100644
--- a/codec/decoder/core/src/manage_dec_ref.cpp
+++ b/codec/decoder/core/src/manage_dec_ref.cpp
@@ -294,6 +294,7 @@ int32_t WelsMarkAsRef (PWelsDecoderContext pCtx) {
       if (iRet != ERR_NONE) {
         if (pCtx->eErrorConMethod != ERROR_CON_DISABLE) {
           iRet = RemainOneBufferInDpbForEC (pCtx);
+          WELS_VERIFY_RETURN_IF (iRet, iRet);
         } else {
           return iRet;
         }
@@ -309,6 +310,7 @@ int32_t WelsMarkAsRef (PWelsDecoderContext pCtx) {
       if (iRet != ERR_NONE) {
         if (pCtx->eErrorConMethod != ERROR_CON_DISABLE) {
           iRet = RemainOneBufferInDpbForEC (pCtx);
+          WELS_VERIFY_RETURN_IF (iRet, iRet);
         } else {
           return iRet;
         }
@@ -320,11 +322,12 @@ int32_t WelsMarkAsRef (PWelsDecoderContext pCtx) {
     if (pRefPic->uiLongRefCount[LIST_0] + pRefPic->uiShortRefCount[LIST_0] >= WELS_MAX (1, pCtx->pSps->iNumRefFrames)) {
       if (pCtx->eErrorConMethod != ERROR_CON_DISABLE) {
         iRet = RemainOneBufferInDpbForEC (pCtx);
+        WELS_VERIFY_RETURN_IF (iRet, iRet);
       } else {
         return ERR_INFO_INVALID_MMCO_REF_NUM_OVERFLOW;
       }
     }
-    AddShortTermToList (pRefPic, pCtx->pDec);
+    iRet = AddShortTermToList (pRefPic, pCtx->pDec);
   }
 
   return iRet;
@@ -515,6 +518,15 @@ static int32_t AddShortTermToList (PRefPic pRefPic, PPicture pPic) {
   pPic->bIsLongRef = false;
   pPic->iLongTermFrameIdx = -1;
   if (pRefPic->uiShortRefCount[LIST_0] > 0) {
+    // Check the duplicate frame_num in short ref list
+    for (int32_t iPos = 0; iPos < pRefPic->uiShortRefCount[LIST_0]; iPos++) {
+      if (pPic->iFrameNum == pRefPic->pShortRefList[LIST_0][iPos]->iFrameNum) {
+        // Replace the previous ref pic with the new one with the same frame_num
+        pRefPic->pShortRefList[LIST_0][iPos] = pPic;
+        return ERR_INFO_DUPLICATE_FRAME_NUM;
+      }
+    }
+
     memmove (&pRefPic->pShortRefList[LIST_0][1], &pRefPic->pShortRefList[LIST_0][0],
              pRefPic->uiShortRefCount[LIST_0]*sizeof (PPicture));//confirmed_safe_unsafe_usage
   }