diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index 159b7b15..851d0d08 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -2244,7 +2244,7 @@ size_t ZSTD_estimateDStreamSize(size_t windowSize)
     size_t const blockSize = MIN(windowSize, ZSTD_BLOCKSIZE_MAX);
     size_t const inBuffSize = blockSize;  /* no block can be larger */
     size_t const outBuffSize = windowSize + blockSize + (WILDCOPY_OVERLENGTH * 2);
-    return sizeof(ZSTD_DStream) + ZSTD_estimateDCtxSize() + inBuffSize + outBuffSize;
+    return ZSTD_estimateDCtxSize() + inBuffSize + outBuffSize;
 }
 
 ZSTDLIB_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize)