diff --git a/lib/compress/huf_compress.c b/lib/compress/huf_compress.c
index 485906e678a..e9cb0bd5f55 100644
--- a/lib/compress/huf_compress.c
+++ b/lib/compress/huf_compress.c
@@ -133,6 +133,7 @@ size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize,
         wksp->huffWeight[n] = wksp->bitsToWeight[CTable[n].nbBits];
 
     /* attempt weights compression by FSE */
+    if (maxDstSize < 1) return ERROR(dstSize_tooSmall);
     {   CHECK_V_F(hSize, HUF_compressWeights(op+1, maxDstSize-1, wksp->huffWeight, maxSymbolValue, &wksp->wksp, sizeof(wksp->wksp)) );
         if ((hSize>1) & (hSize < maxSymbolValue/2)) {   /* FSE compressed */
             op[0] = (BYTE)hSize;
diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 70f1693574b..9e814e31d1d 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -3486,6 +3486,7 @@ static size_t ZSTD_compressSeqStore_singleBlock(ZSTD_CCtx* zc, seqStore_t* const
     if (isPartition)
         ZSTD_seqStore_resolveOffCodes(dRep, cRep, seqStore, (U32)(seqStore->sequences - seqStore->sequencesStart));
 
+    RETURN_ERROR_IF(dstCapacity < ZSTD_blockHeaderSize, dstSize_tooSmall, "Block header doesn't fit");
     cSeqsSize = ZSTD_entropyCompressSeqStore(seqStore,
                 &zc->blockState.prevCBlock->entropy, &zc->blockState.nextCBlock->entropy,
                 &zc->appliedParams,